1. Introduction

Paleozoic brachiopods have been rarely used as biostratigraphic markers because of their benthic lifestyle and their preference for shallow water settings. These environments are generally unfavourable for traditional markers such as graptolites and conodonts, but in the absence of such fossils, brachiopods can be potentially useful to establish a chronology (e.g., Ziegler, 1966; Baarli and Johnson, 1988; Laurie, 1991; Jin, 2001; Reyes-Abril et al., 2011; Sohrabi and Jin, 2013), as well as for locating systemic boundaries (e.g., Mottequin et al., 2014; Angiolini et al., 2021).

The first brachiopod-based biostratigraphic scheme for southwestern Gondwana was proposed by Herrera and Benedetto (1991), who erected five “assemblage” biozones through the Tremadocian-Darriwilian carbonate succession of the Precordillera basin of western Argentina. These biozones proved to be useful for intrabasinal correlations and, to a lesser extent, for correlations with neighboring (e.g., Famatina) basins. They were further redefined as “taxon-range” biozones and their taxonomic composition was updated (Benedetto, 2002). Although the set of taxa recorded in each biozone reflects primarily the evolution of brachiopod lineages through time, it is also conditioned by the environmental changes that took place in the basin, as well as by the relative paleogeographic placement of the far-travelled Precordillera terrane through time (Benedetto, 1998a, 2007a; Benedetto et al., 1999). The sum of these biologic, climatic and tectonic factors allowed each taxon-range biozone to experience some taxonomic variability and often some degree of diachronism through the basin.

A rather different biostratigraphic scheme based on “lineage biozones” or “phylozones” was proposed later for the Furongian-Lower Ordovician successions of northwestern Argentina (Benedetto, 2005). A lineage biozone, according to the definition of the North American Stratigraphic Code (2005, p. 1574) is “...a body of rock containing species representing a specific segment of an evolutionary lineage”. The successive taxa forming the evolutionary lineage constitute a powerful tool to establish biostratigraphic schemes, in particular in those cases where morphological changes along the lineage concentrate in short periods of time, and the new evolved species remain nearly unchanged (morphological stasis) until the next speciation event. Most lineages usually split in two, originating new species in the process of cladogenesis. In the example posed here, coexistence in the same stratigraphic horizon of ancestral and descendent species has not been observed, so that the simplest scenario is one in which a single lineage punctuated by phenotypic changes (punctuated anagenesis; see Jackson and Cheetham, 1999) spreads throughout the basin. However, the fact that closely allied species of Kvania are present in upper Tremadocian rocks of central Europe (e.g., Havlíček, 1994; Szduy et al., 2001), coexisting with or postdating the more derived members of the Andean lineage (e.g., Gondwanorthis and Lampazarorthis), strongly suggests the occurrence of one or more cladogenetic events in the region, as the cladistic analysis of plectorthoids performed by Benedetto and Muñoz (2017) demonstrated. On the other hand, there is no conclusive evidence of the so-called “punctuated gradualism”, in which a lineage shows both punctuation and gradual change (Fortey, 1988) since no morphological transition between ancestral and descendent species has been observed in the lineage under consideration. However, since distinction of the terms “gradual” and “rapid” when applied to morphologic evolution in the fossil record is ambiguous and has been subject to varying interpretations by different authors, an explicit, statistical analysis is necessary to comprehensively define the evolutionary pattern (Hunt, 2008).

The time interval covered by the successive species of a lineage can vary somewhat, but it can be usually as short as the conodont or graptolite biozones. A further advantage of phylozones is that, due to the nature of evolutionary process, there should be no significant overlap in the ranges of ancestral and descendent species along the lineage. However, this is not always the case, being true only in those lineages showing an anagenetic (punctuated or gradual) pattern. For instance, in the Upper Ordovician of Laurentia, the older and smaller species of Zygospira co-existed with younger species that evolved throughout the Katian, which is interpreted as a case of sympatric speciation where a single ancestral species gave rise to new species probably by niche partitioning (Sproat and McLeod, 2023). In the Kvania example from above, nevertheless, there is no evidence that Kvania lariensis coexisted neither with the ancestral species K. primigenia nor with the descendent K. azulpampensis, although further research at the basin scale is needed to fully clarify the evolutionary pattern.

As in other biostratigraphic units, in the phylozones the boundaries are surfaces that mark the lowest (first appearance datum; FAD) and highest (last appeareance datum; LAD) occurrence of successive taxa along the evolutionary lineage. Whenever the lowest appearance of successive segments in a lineage over the area of their distribution can be considered as basically synchronous, the lineage zones allow precise correlations to be established (Tanaka and Takahasi, 2013). In the practice, however, identification of such evolutionary lineages is not always possible since it requires of a nearly uninterrupted stratigraphic succession lacking abrupt environmental shifts and, most importantly, an essentially continuous series of phylogenetically linked taxa. In northwestern Argentina, the ~3,500 m-thick platform and shoreface clastic successions of the Santa Victoria Group (Waisfeld et al., 2023, and references therein) constitutes an excellent case study since rhynchonelliform brachiopods of Late Cambrian to late Floian age are abundant in there and well preserved throughout the unit (Benedetto, 1998b, 2007b; Benedetto and Carrasco, 2002; Harper et al., 2004; Villas and Herrera, 2004; Villas et al., 2009; Muñoz and Benedetto, 2016; Benedetto and Muñoz, 2017). Also interesting is that fossiliferous levels often include more or less continuous series of early juvenile to gerontic individuals, allowing to reconstruct the ontogenetic trajectories of some species and hence to infer morphological trends directed by heterochronic processes (Benedetto, 2007b).

In this contribution, Kvania lariensis Benedetto is reported for the first time from the Eastern Cordillera of the Jujuy Province, from beds of well constrained earliest Tremadocian age (Tr1). The species K. lariensis is a basal form within the Furongian-Early Ordovician Protorthisina-Kvania-Gondwanorthis-Lampazarorthis-Tarfaya plectorthoid lineage (Benedetto and Muñoz, 2017). The presence of K. lariensis in widely separated localities of the Altiplano-Puna region and the Eastern Cordillera of Bolivia and northwestern Argentina, along with its well-constrained conodont and graptolite-based age, leaves this species as a useful biostratigraphic marker for the lowermost Ordovician of the Central Andean basin of Gondwana. Moreover, other taxa of this phylogenetic lineage, in particular the descending species Kvania azulpampensis and Gondwanorthis calderensis calderensis also constitute regional index fossils. The purpose of this contribution is therefore to review and update available chronostratigraphic information since the first attempt of a brachiopod-based biozonation for the Ordovician of the Central Andean basin (Benedetto, 2005), and also to propose the species K. primigenia as a reliable biostratigraphic marker for the upper Furongian. Finally, equivalences among the brachiopod-based and the trilobite-based biostratigraphic schemes are examined.

2. Geological setting

Lower Paleozoic rocks in northwestern Argentina and southwestern Bolivia are superbly exposed in the vast Central Andean basin encompassing the Eastern Cordillera and the Subandean Ranges (e.g., Astini, 2003; Waisfeld et al., 2023) (Fig. 1). The Puna-Famatina magmatic arc developed to the west is characterized by thick volcanic and sedimentary successions (Coira et al., 1999). In northern Chile, to the south of Salar de Atacama, there are also extensive outcrops of Ordovician volcanic, intrusive, and sedimentary rocks (Niemeyer, 1989).

Fig. 1. Map showing the main exposures of the Santa Victoria Group (Furongian-Lower Ordovician) in the Central Andean basin of northwestern Argentina. Upper left map, location of the (1) Subandean Ranges, (2) Eastern Cordillera, and (3) Altiplano-Puna. In the main and bottom left maps, the black stars indicate the localities yielding species of Kvania and Gondwanorthis referred to in the text (see central left map for regional locations). In the bottom left map, yellow areas indicate saline basins. The main roads (black lines) and towns (black circles) are indicated in the main map. The study area (Quebrada Salto Alto) is located at 23°45’ S and 65°28’ W.

An extensional phase during the Late Cambrian led to deposition in the Eastern Cordillera of the Mesón Group, which consists of Skolithos-rich reddish sandstones and siltstones deposited in tide-dominated environments (e.g., Mángano and Buatois, 1999, 2004). During the latest Cambrian (Furongian, Stage 10) and earliest Ordovician (Tremadocian, Tr1), the establishment of the Puna-Famatinian magmatic arc along the convergent proto-Andean margin, and the subsequent transition from an extensional basin to a retroarc basin, led to deposition of more than 3,500 m-thick marine clastic rocks, now part of the Santa Victoria Group. This succession was affected not only by sea-level fluctuations (e.g., Astini, 2003; Buatois and Mángano, 2003; Buatois et al., 2006) but also by tectonic uplifts due to the arc emplacement (e.g., Bahlburg and Hervé, 1997; Vaucher et al., 2020). Regionally, the Mesón Group is unconformably overlain by the Santa Victoria Group (Turner, 1960), which includes the Santa Rosita (Furongian-Tremadocian) and Acoite (Floian) formations. The Santa Rosita Formation has been formally subdivided into six members named, from base to top: Tilcara, Casa Colorada, Pico de Halcón, Alfarcito, Rupasca, and Humacha (Buatois and Mángano, 2003). The Tilcara and Pico de Halcón members record sedimentation in tidal-dominated settings, filling incised valleys, whereas the Casa Colorada, Alfarcito, and Rupasca members were deposited in wave-dominated open-marine environments, punctuated by storm events.

The Quebrada Salto Alto, from which the studied specimens of Kvania lariensis come from, is located a few kilometers to the east of the Purmamarca town, on the east side of the Río Grande, which runs along the extensive Quebrada de Humahuaca valley (Figs. 1, 2A and B). There, the stratigraphic section starts with the Pico de Halcón Member consisting of several meters of thick-bedded, tabular, and cross-stratified sandstones interpreted as recording subtidal sandbars (Buatois and Mángano, 2003) (Fig. 2C, D). They are overlain in sharp contact by the heterolithic fine-grained deposits of the Alfarcito Member, interpreted as reflecting an extensive transgression flooding an estuarine valley (Buatois et al., 2006). Downstream the Quebrada Salto Alto, the stratigraphic section is faulted and folded so that the preserved thickness of the member reaches about 120 m, approximately half as thick as those in other less deformed sections along the Quebrada de Humahuaca (e.g., Rupasca section). The lower part of the Alfarcito Member is characterized by mudstones and greenish-gray fine-grained rippled sandstones, which represent offshore deposits accumulated in a low-gradient platform affected by fairweather and storm waves (Buatois et al., 2006). A few meters above the base of this member there is a conspicuous ~30 m-thick interval of black shales and fossiliferous, pyrite-rich calcareous mudstones and calcarenites (Fig. 2C, D) partly corresponding to the Purmamarca shales of Harrington and Leanza (1957). These beds yielded well preserved specimens of Kvania lariensis, Jujuyaspis keideli Kobayashi, conodonts (Zeballo and Albanesi, 2009), and linguliformean brachiopods (siphonotretids and obolids). The succession continues with ~80 m of interbedded hummocky cross-stratified fine-grained sandstones and mudstones, the lower ~30 m bearing shell concentrations of Kvania lariensis, obolid brachiopods, and trilobites (Jujuyaspis keideli and Asaphellus communis).

Fig. 2. A. Satellite general view of the study area (see Fig. 1 for a general location). B. Zoom-in excerpt into the Quebrada Salto Alto showing the stratigraphic section (white line) and fossiliferous beds location (black asterisk). C. Headwaters of the Quebrada Salto Alto toward the east, showing the Pico de Halcón and the Alfarcito members. Black asterisk indicates the location of the fossiliferous beds. D. Detail of the sharp contact between the Pico de Halcón and the Alfarcito members (note that the succession is overturned). In the foreground, fossiliferous black shales with calcareous concretions yielding Kvania lariensis and Jujuyaspis keideli.

3. The Protorthisina-Kvania-Gondwanorthis phylogenetic lineage

The numerous and well-preserved plectorthoid brachiopods recovered from the Upper Cambrian-Floian successions of the Central Andean basin led to recognition of the Protorthisina-Kvania-Gondwanorthis-Lampazarorthis-Tarfaya phylogenetic lineage (Benedetto and Muñoz, 2017). Beside cladistic analysis, this evolutionary lineage is supported by ontogenetic evidence, showing that successive taxa display increasingly peramorphic characters affecting shell size, ornament, and internal structures. These findings favored the hypothesis that morphological changes through time were mainly directed by the heterochronic process of peramorphosis (Benedetto, 2007b), consequently constituting a peramorphocline (McNamara, 1990).

The phylogenetic hypothesis supports that the endemic species Protorthisina simplex is the ancestral form, which gave rise successively to Kvania primigenia Benedetto, Kvania lariensis Benedetto, Kvania azulpampensis Benedetto, and Gondwanorthis calderensis (Benedetto) (Benedetto, 2007b; Benedetto and Muñoz, 2017), thus bracketing the Furongian-lower Tremadocian in the Central Andean basin (Fig. 3). The younger members of the lineage of late Tremadocian-Floian age, Lampazarorthis bifurcata (Harrington), L. alata Benedetto and Muñoz, Tarfaya purmamarcaensis (Benedetto), and Tarfaya grandis (Harrington), will be considered in a further analysis, as they are likely to be useful markers for the upper Tremadocian/Floian of the region.

 

Fig. 3. Biostratigraphic chart and brachiopod phylozones for the Tremadocian of the Central Andean Basin. Data on conodonts from Rao and Hünicken (1995), Ortega and Albanesi (2005), and Waisfeld et al. (2023, and references therein); trilobite biozones from Vaccari et al. (2010). Dotted line indicates that the boundary between Protorthisina simplex and Kvania primigenia is yet to be established (note that P. simplex has not been proposed formally as a phylozone).

Figure 4 shows the species succession and morphologic changes that took place through the Furongian and early Tremadocian of the Central Andean basin. Protorthisina simplex is likely to be the basal taxon of the lineage. It is characterized externally by its minute subcircular shell ornamented by few, up to ten simple ribs, occasionally dichotomized distally. Internally it is distinguished by the brachiophore bases forming a minute septalium. The inferred descendent species Kvania primigenia has a somewhat larger shell and the rib number increases to 18-20. Internally, the septalium is larger than in Protorthisina and, in later growth stages, brachiophore plates become separated medially (Benedetto, 2007b). This species is morphologically intermediate between P. simplex and the succeeding Kvania lariensis, in which the rib number increases to 25-30, and the brachiophore bases tend to become subparallel or slightly convergent anteriorly forming a narrow subrectangular notothyrial chamber (Figs. 4 and 5). The latter feature is considered diagnostic of the genus Kvania. The next step in the evolutionary lineage is represented by Kvania azulpampensis, which always occurs above the last documented appearance of K. lariensis. This species is larger than K. lariensis and the costellae are more numerous, totalizing up to 45 (Fig. 4). Although the dorsal interiors of both species are quite similar, the notothyrial chamber in K. azulpampensis is well developed at all ontogenetic stages. According to the phylogenetic hypothesis detailed here, K. azulpampensis gave origin to Gondwanorthis calderensis (Benedetto), whichis characterized by a variably fascicostellate or parvicostellate ornament forming well-defined bundles distally, the number of costellae counted at valve margin ranging from 65 to 78. The notothyrial chamber in juvenile individuals is small and subrectangular, and it is delimited by blade-like, subparallel brachiophpore plates. As they grow, the lateral apical cavities become gradually filled by secondary deposits masking the brachiophore bases, which are now confined to the posterior part of the notothyrial platform (Fig. 4). It is remarkable that juvenile specimens of G. calderensis strongly resemble the adults of Kvania azulpampensis in their subrectangular notothyrial chamber flanked by long subparallel brachiophore bases, which suggests that G. calderensis originated by peramorphy from K. azulpampensis (Benedetto and Muñoz, 2017).

Fig. 4. Phylogenetic lineage of the species discussed in the text showing morphological evolution of the exterior (left) and interior (right) of the dorsal valves (modified from Benedetto, 2007b, and Benedetto and Muñoz, 2017). Scale bars represent 1 mm.

Fig. 5. Kvania lariensis from Quebrada Salto Alto, lower part of the Alfarcito Member, Santa Rosita Formation. A. Dorsal valve exterior, juvenile specimen CEGH-UNC 27670. B. Dorsal valve exterior, young adult specimen, CEGH-UNC 2776. C. Dorsal valve exterior, CEGH-UNC 27662. D. Dorsal valve exterior, CEGH-UNC 24671. E. Ventral valve exterior, latex cast CEGH-UNC 27775. F. Dorsal valve exterior, CEGH-UNC 27663. G. Dorsal valve exterior, CEGH-UNC 27773. H. Dorsal valve exterior, CEGH-UNC 27661a. I. Ventral valve exterior CEGH-UNC 27672. J. Ventral valve exterior, CEGH-UNC 27660. K. Ventral valve exterior CEGH-UNC 27673. L. Ventral valve exterior CEGH-UNC 27661b. M. Ventral valve exterior CEGH-UNC 27669. N. Ventral valve interior, CEGH-UNC 27664b. O. Ventral valve internal mold, CEGH-UNC 27665a. P-Q. Dorsal valve internal mold and latex cast CEGH-UNC 27667. R. Dorsal valve interior CEGH-UNC 27665b. S. Dorsal valve interior CEGH-UNC 27674. T-U. Dorsal valve interior, and detail of cardinalium, CEGH-UNC 27668. V. Dorsal valve interior, CEGH-UNC 27664a. W-X. Kvania lariensis, specimens from the Las Vicuñas Formation (Quebrada Lari). W. Dorsal valve latex cast, detail of cardinalium, CEGH-UNC 18951. X. Internal mold of dorsal valve, holotype CEGH-UNC 18948b (from Benedetto, 2007b). Scale bars represent 1 mm. Figured specimens prefixed CEGH-UNC are stored in the paleontological collection of CICTERRA (Centro de Investigaciones en Ciencias de la Tierra, CONICET-UNC), Córdoba, Argentina.

4. Kvania lariensis in time and space

Kvania lariensis Benedetto was described originally from the early Tremadocian Las Vicuñas Formation exposed in the Quebrada Lari, north from the Salar de Arizaro in the western Puna region, a few kilometers from the Chilean border (Fig. 1). In that location, the rocks are intensely folded and faulted and their bases remain unknown. They are unconformably overlain by marine shales and sandstones of latest Ordovician-Early Silurian age (Isaacson et al., 1976; Benedetto and Sánchez, 1990; Rubinstein and Vaccari, 2004).

The Las Vicuñas Formation consists of a lower interval of pyroclastic rocks overlain in sharp contact by a thin bed of fossiliferous calcareous sandstones followed by ~70 m of green shales and mudstones. The type material of K. lariensis comes from the lower interval of green shales faulted against the base of the pyroclastic beds, which also contain Pseudokainella n. sp. aff. conica Kobayashi (formerly referred to as Kainella sp. by Moya et al., 1993; see Vaccari and Waisfeld, 2000). The basal calcareous sandstones have yielded conodonts, graptolites, and in particular trilobites of early Tremadocian age, which incluyde Geragnostus aff. intermedius Palmer, Asaphellus communis Robison and Pantoja, Leiostegium douglasi Harrington, Australoharpes sp., Onychopyge sp., Amzaskiella sp., and Conophrys fabiani Waisfeld et al. (Moya et al., 1993; Malanca et al., 1998; Vaccari and Waisfeld, 2000; Waisfeld et al., 2001). These levels also contain the graptolites Staurograptus sp. and Rhabdinopora sp.

The upper green shales of the Las Vicuñas Formation have been referred tentatively to the Rhabdinopora flabelliformis parabola Zone, the    second graptolite zone of the Tremadocian Stage (Giuliano et al., 2013). Several calcarenitic levels in there have yielded the conodonts Cordylodus caboti Bagnoli, Barnes and Stevens, Cordylodus intermedius Furnish, and Phakelodus tenuis (Müller) (Rao et al., 2000); more recently, Giuliano et al. (2013) documented from the same beds Cordylodus lindstromi Druce and Jones, C. proavus Müller, C. deflexus Bagnoli, Barnes and Stevens, and Teridontus nakamurai (Nogami). Such conodont association is indicative of an early Tremadocian age. Therefore, the sum of evidence from the Quebrada Lari stratigraphic section allows placement of K. lariensis at the base of the Tremadocian. Data from other localities where this species has been recorded confirm this age placement. For instance, in the Taique Formation at Sierra del Cobre, ~25 km east of Susques (Fig. 1), K. lariensis is associated with the trilobite Jujuyaspis keideli, a well-established biostratigraphic marker of the base of the Ordovician System in the Central Andean basin (Tortello et al., 2002; Vaccari et al., 2010; Waisfeld et al., 2023, and references therein). In the Ronqui Angosto section, in the westernmost ranges of the Eastern Cordillera (Fig. 1), a few specimens of K. lariensis have been found ~80 m above the record of Protorthisina simplex, of undoubtedly Furongian age (Parabolina (Neoparabolina) frequens argentina Zone). In the Eastern Cordillera of southwestern Bolivia, in turn, a few specimens of K. lariensis have been identified in the Iscayachi Formation. A recent revision of the trilobites from this unit at Cuesta de Erquis, ~10 km northwest of Tarija, revealed the presence of an assemblage belonging to the lower part of the Jujuyaspis keideli Biozone (lowermost Tremadocian, Tr1), which lies immediately above levels bearing Parabolina (Neoparabolina) frequens of Furongian age (Vaccari et al., 2018).

The material reported in this paper is the first record of K. lariensis in the Quebrada de Humahuaca region (Figs. 1 and 2). In the Quebrada Salto Alto section, like most places, it is associated with Jujuyaspis keildeli, which designates a biozone widely distributed in the Central Andean basin marking the base of the Ordovician System (Tortello et al., 2002; Vaccari et al., 2010). Conodonts from the calcareous mudstones yielding K. lariensis were referred by Zeballo and Albanesi (2009) to the Late Cambrian Cordylodus intermedius Biozone (Hirsutodontus simplex Subzone). However, although in certain localities (e.g., Texas and Utah, United States) H. simplex is restricted to the Furongian (Miller et al., 2006), in the Green Point GSSP (Newfoundland, Canada) it has been recorded above the first record of Iapetognathus fluctivagus, the primary marker of the base of the Ordovician System (Barnes, 1988; Cooper et al., 2001). So, H. simplex should be rejected as a marker for the uppermost Cambrian (see discussion in Terfelt et al., 2012).

In accordance with the chronologic evidence mentioned above, K. lariensis is proposed here as a marker species for the base of the Ordovician in the Central Andean basin. As figure 3 shows, this phylozone is considered time-equivalent to the Jujuyaspis keideli trilobite biozone.

5. The lower Tremadocian brachiopod lineage biozones

Based on the previously exposed phylogenetic evidence, two other phylozones can be recognized within the time slice Tr1 (Bergström et al., 2009), the Kvania azulpampensis and the Gondwanorthis calderensis calderensis biozones. As figure 3 shows, they are almost equivalent to the Kainella andina and Kainella meridionalis trilobite biozones (as redefined by Vaccari et al., 2010), respectively, and to the Cordylodus angulatus conodont Zone. These two phylozones are described below.

5.1. The KvaniaazulpampensisPhylozone

The type material of K. azulpampensis was recovered approximately 1 km north of the National Road 9 in the Azul Pampa region (Fig. 1), from grey and reddish pink fossiliferous sandstones in the transition between the Casayok and Azul Pampa Formations (Harrington and Leanza, 1957; Fernández, 1985). The succession of mudstones and cross-bedded fine-grained sandstones bearing reworked brachiopod shells, trilobite sclerites, and trace fossils, was referred subsequently to the Alfarcito Member of the Santa Rosita Formation, whereas the overlying parallel-laminated green mudstones (the Azul Pampa Formation) were re-assigned to the Acoite Formation (Such et al., 2007). In the Alfarcito Member, K. azulpampensis is associated with the trilobites Leptoplastides marianus Harrington and Leanza and Kainella andina. K. azulpampensis has also been recorded in the upper part of the Pupusa Formation (formerly considered as part of the Cardonal Formation, see Vaucher et al., 2020) exposed at Quebrada Amarilla in the Sierra de Cajas (Fig. 1), where it is associated with K. andina. In this section, the first appearance datum (FAD) of K. andina lies ~15 m above the last record of Jujuyaspis keideli (Vaccari et al., 2010). These beds also mark the FAD of Anisograptus matanensis, which occurs a few meters above the first record of Rhabdinopora flabelliformis cf. parabola (Albanesi and Ortega, 2016).

5.2. The Gondwanorthis calderensis calderensisPhylozone

In the Eastern Cordillera, the genus Gondwanorthis is one of the most common taxa in strata of late early Tremadocian age. The genus was erected to include some species formerly attributed to the genus Nanorthis (Benedetto, 2007b). The type species Gondwanorthis calderensis (Benedetto) occurs in many localities of the Eastern Cordillera in strata of early Tremadocian age. In the La Caldera stratotype at the Sierra de Mojotoro, north of Salta City (Fig. 1), this species is associated with trilobites of the Kainella meridionalis Zone. In the Parcha locality of the Quebrada del Toro, west of Salta City (Fig. 1), Gondwanorthis calderensis calderensis is very abundant in fossil-rich boulders redeposited from the underlying shallow-water cross-bedded sandstones of the Cardonal Formation (see Astini, 2003), which also bear K. meridionalis and conodonts of the Cordylodus angulatus Biozone (Tortello and Rao, 2000).

The subspecies G. calderensis alternata has been recorded in the uppermost part of the Pupusa Formation in the Angosto del Moreno and Sierra de Cajas sections (Fig. 1), associated also with conodonts of the Cordylodus angulatus Zone (Rao and Hünicken, 1995; Rao and Tortello, 1998; Rao, 1999; Tortello et al., 1999; Moya et al., 2003). In the Angosto del Moreno stratigraphic section, G. calderensis alternata occurs in cross-stratified sandstones and densely packed shell concentrations bearing the rhynchonelliform Chaniella pascuali Benedetto and the linguliform brachiopods Torobolus cf. subplanus Benedetto and Muñoz, Eurytreta harringtoni Mergl and Herrera, and Celdobolus skrikus Lavié and Benedetto (Benedetto, 2009; Lavié and Benedetto, 2023). These beds also yielded Kainella morena, which according to Vaccari et al., 2010 is suggestive of the Kainella andina Zone.  However, as these authors noted, there is some uncertainty about the exact stratigraphic position of these Kainella species because they have not been documented in the same stratigraphic section. In the Sierra de Cajas (Quebrada de la Vizcacha), G. calderensis alternata occurs near the top of the Pupusa Formation, a few meters above the last appearance of Kvania azulpampensis,supporting a direct ancestor-descendent relationship between the two species.

6. The new Furongian Kvania primigenia lineage Biozone

As stated previously, Protorthisina simplex is the basal form of the lineage. Its biostratigraphic significance is currently limited by the fact that until the present this species has been found in a single locality and for this reason it has not yet formally proposed as a new biozone. Its Furongian age, however, is beyond doubt and it has been included in the biostratigraphic chart of figure 3. On the contrary, Kvania primigenia has been recorded in different localities of the Eastern Codillera, in all cases associated with the trilobite Parabolina (Neoparabolina) frequens argentina (Kayser), which is considered a reliable biostratigraphic marker for the Furongian (Stage 10) of the Central Andean basin (Tortello and Rao, 2000; Tortello et al., 2002; Tortello and Esteban, 2003; Vaccari et al., 2010). The type material of K. primigenia comes from dark gray siltstones of the Lampazar Formation at Quebrada Totora (Fig. 1). It also occurs in carbonate lenses within the Lampazar Formation exposed along the old trace of National Road 16 (upper Pumamarca river), in fine-grained sandstones from the lower part of the Santa Rosita Formation (Azul Pampa region) (Such et al., 2007), and in calcareous mudstones exposed at the eastern slope of Sierra de Cajas, in Quebrada Vizcacha, ~130 m above the Padrioc Formation sandstones (Fig. 1). In addition, the Upper Cambrian conodont Cordylodus proavus was first reported from these calcareous beds by Rao and Hünicken (1995) and confirmed by subsequent studies (Albanesi and Ortega, 2002; Albanesi et al., 2008, 2015, and references therein). Based on all the available evidence, K. primigenia is proposed here as a phylozone, marking the uppermost Cambrian in the Central Andean basin (Fig. 3).  

7.  Additions to the morphology of Kvania primigenia and K. lariensis

The numerous specimens of Kvania lariensis from the earliest Tremadocian Alfarcito Member in the Quebrada Salto Alto provide new information about its phenotypic variablity (Fig. 5). Morphologically, the new sample of Kvania lariensis from the Quebrada Salto Alto does not differ significantly from the type material collected farther west, from the Quebrada Lari area in the western Puna region. The latter, however, is by far much less numerous than the studied sample, so its range of morphological variation cannot be established as accurately. Adult shells from the studied locality are, on average, slightly larger than those from Quebrada Lari, ranging from 3.7 to 6.5 mm in width (in the type specimen”s it ranges from 3.0 to 4.3 mm). Unlike the type material from Quebrada Lari, which includes a single conjoined juvenile specimen (Fig. 7.1 in Benedetto, 2007b), in the studied sample juvenile shells of both valves are relatively frequent. In addition, there are some valves corresponding to young adults and others to large adults, so a reconstruction of the ontogenetic series in possible. Smaller individuals (3.7-3.9 mm in width) are characterized by few (5-6) simple primary costellae dichotomized distally to reach a total of 16-18 at valve margin (Fig. 5A, B). Intermediate ontogenetic stages display 10-11 primary costellae, generating by dichotomy 20-23 costellae at the margin (Fig. 5C). In large adults, primary costae split for a second time at about two-third of valve length, reaching in total ~35 costellae at valve margin. These specimens also show some costellae interpolated between the bundles, especially in the dorsal valve (Fig. 5F, G). In this respect, the material of K. lariensis from the Alfarcito Member confirms the trend of increasing number of costellae through ontogeny observed in the type material. This also corrobotates that the lineage as a whole experienced a defined evolutionary trend towards an increase in both shell size and costellae number (Benedetto, 2007b). Internally, the studied material is nearly identical to the type material (compare Fig. 5U and W). Adult specimens from both localities show subparallel brachiophore bases converging onto the valve floor to form a small subrectangular notothyrial chamber (Fig. 5R-T). An incipient septalium, however, can be developed in juvenile individuals (Fig. 5P and Q), as in the adults of the ancestral species K. primigenia, supporting its origin by heterochrony. 

Concerning the Furongian species K. primigenia, a generic assignement is difficult since it exhibits intermediate features between the inferred ancestor Protorthisina simplex and its descendent Kvania lariensis. K primigenia differs from P. simplex mainly in the branching of primary ribs near the mid-valve length and, internally, in its proportionally larger septalium not supported by a septum. Originally, the author questionably referred the type material to Kvania because of its fascicostellate ornament rather than simple ribbing, and the fact that in adult specimens the brachiophore bases converge onto the valve floor forming a notothyrial chamber (Benedetto 2007b, p. 277). However, since a true septalium is absent (excepting in some juvenile specimens) and a well-defined subtriangular to subrectangular notothyrial chamber (considered a diagnostic feature of Kvania) is always present, the species primigenia is herein assigned to Kvania without interrogation.

8. Conclusions

Species forming an evolutionary lineage are key to establishing biostratigraphic schemes. In the Central Andean basin of South America, the well-established Protorthisina-Kvania-Gondwanorthis brachiopod lineage evolved across the Cambrian-Ordovician boundary. On the basis of well-constrained ages and regional distribution of the successive species, four phylozones are recognized. The species Kvania primigenia is proposed as a reliable marker of the uppermost Cambrian, spanning a time almost equivalent to that of the Parabolina (Neoparabolina) frequens argentina trilobite zone. The species Kvania lariensis is reported for the first time from the Eastern Cordillera of Jujuy from beds of well-constrained earliest Tremadocian (Tr1) age. Its presence in the western and eastern Puna regions and in the Eastern Cordillera of Bolivia and northwestern Argentina, along with its well-known conodont-based and graptolite-based age leaves this species as a useful marker for the lowermost Ordovician in the region. The K. lariensis and K. azulpampensis phylozones are recognized within the time slice Tr1, and are almost time-equivalent to the Jujuyaspis keideli and Kainella andina trilobite biozones, respectively. Finally, the descendent subspecies Gondwanorthis calderensis calderensis is considered coeval to the Kainella meridionalis Biozone, marking the upper part of the Tr1 time slice.

Acknowledgments
I thank my colleagues D. Balseiro, for making available its collection from the Alfarcito member at the Quebrada Salto Alto, and E. Vaccari and B. Waisfeld for their comments on the stratigraphy and trilobite biozones of the Cordillera Oriental. Financial support was provided by the “Agencia Nacional de Promoción Científica y Tecnológica” to B.A. Toro (PICT 2020-02853), and by the Consejo Nacional de Investigaciones Científicas y Técnicas to B. Waisfeld (PIP 2020-11220200103192). C. Sproat and F. Tortello helped reviewing this manuscript.

References

Albanesi, G.L.; Ortega, G. 2002. Advances on conodont-graptolite biostratigraphy of the Ordovician System of Argentina. In Aspects of the Ordovician System in Argentina (Aceñolaza, F.G.; editor). Instituto Superior de Correlación Geológica (Insugeo), Serie Correlación Geológica 16: 143-165. Tucumán.

Albanesi, G.L.; Ortega, G. 2016. Chapter Two-Conodont and Graptolite Biostratigraphy of the Ordovician System of Argentina. Stratigraphy & Timescales 1: 61-121. https://doi.org/10.1016/bs.sats.2016.10.002

Albanesi, G.L.; Ortega, G.; Zeballo, F.J. 2008. Faunas de conodontes y graptolitos del Paleozoico inferior de la Cordillera Oriental Argentina. In Geología y Recursos Naturales de la provincia de Jujuy (Coira, B.; Zapettini, E.O.; editors). Relatorio Congreso Geológico Argentino No. 17: 98-118. Buenos Aires.

Albanesi, G.L.; Giuliano, M.; Pacheco, F.E.; Ortega, G.; Monaldi, C.R. 2015. Conodonts from the Cambrian-Ordovician boundary in the Cordillera Oriental, NW Argentina. Stratigraphy 12: 237-256. http://dx.doi.org/10.29041/strat.12.4.03

Angiolini, L.; Cisterna, G.A.; Mottequin, B.; Shu-Zhong, S.; Muttoni, G. 2021. Global Carboniferous brachiopod biostratigraphy. In The Carboniferous Timescale (Lucas, S.G.; Schneider, J.W.; Wang, X.; Nikolaeva, S.; editors). The Geological Society of London, Special Publication 512: 497-550. London. https://doi.org/10.1144/SP512-2020-225

Astini, R.A. 2003. The Ordovician Proto-Andean basins. In Ordovician fossils of Argentina (Benedetto, J.L.; editor). Universidad Nacional de Córdoba, Secretaría de Ciencia y Tecnología: 1-74. Córdoba.

Baarli, B.G.; Johnson, M.E. 1988. Biostratigraphy of key brachiopod lineages from the Llandovery Series (Lower Silurian) of the Oslo Region. Norwegian Journal of Geology 68: 259-274.

Bahlburg, H.; Hervé, F. 1997. Geodynamic evolution and tectonostratigraphic terranes of northwestern Argentina and northern Chile. Geological Society of America Bulletin 109 (7): 869-884. https://doi.org/10.1130/0016-7606(1997)109%3C0869:GEATTO%3E2.3.CO;2

Barnes, C. 1988. The proposed Cambrian-Ordovician global Boundary stratotype and point (GSSP) in Western Newfoundland, Canada. Geological Magazine 125 (4): 381-414. http://dx.doi.org/10.1017/S0016756800013042

Benedetto, J.L. 1998a. Early Palaeozoic brachiopods and associated shelly faunas from western Gondwana: their bearing on the geodynamic history of the pre-Andean margin. In The proto-Andean margin of Gondwana (Pankhurst, R.J.; Rapela, C.W.; editors). The Geological Society of London, Special Publication 142: 57-83. London. https://doi.org/10.1144/GSL.SP.1998.142.01.04

Benedetto, J.L. 1998b. Early Ordovician (Arenig) brachiopods from the Acoite and Sepulturas formations, Cordillera Oriental, northwestern Argentina. Geologica et Palaeontologica 32: 7-27.

Benedetto, J.L. 2002. The Ordovician brachiopod faunas of Argentina: chronology and biostratigraphic succession. In Aspects of the Ordovician System in Argentina (Aceñolaza, F.G.; editor). Instituto Superior de Correlación Geológica (Insugeo), Serie Correlación Geológica 16: 87-106. Tucumán.

Benedetto, J.L. 2005. Hacia un esquema bioestratigráfico de alta resolución para el Cámbrico Superior-Ordovícico del noroeste de Argentina basado en filozonas de braquiópodos rhynchonelliformes. In Congreso Geológico Argentino, No. 16, Actas 3: 371-378. La Plata.

Benedetto, J.L. 2007a. Brachiopod succession in the Lower-Middle Ordovician carbonate platform of the Precordillera terrane, western Argentina: an example of interplay between environmental, biogeographic and evolutionary processes. Acta Palaeontologica Sinica 46: 28-36.

Benedetto, J.L. 2007b. New Upper Cambrian-Tremadoc rhynchonelliformean brachiopods from northwestern Argentina: evolutionary trends and early diversification of plectorthoideans in the Andean Gondwana. Journal of Paleontology 81 (2): 261-285. http://dx.doi.org/10.1666/0022-3360(2007)81[261:NUCRBF]2.0.CO;2

Benedetto, J.L. 2009. Chaniella, a new lower Tremadocian (Ordovician) brachiopod from northwestern Argentina and its phylogenetic relationships with basal rhynchonelliforms. Paläontologische Zeitschrift 83: 393-405. https://doi.org/10.1007/s12542-009-0023-7

Benedetto, J.L.; Sánchez, M.T. 1990. Fauna y edad del estratotipo de la Formación Salar del Rincón (Eopaleozoico, Puna Argentina). Ameghiniana 27 (3-4): 317-326.

Benedetto, J.L.; Carrasco, P. 2002. Tremadoc (earliest Ordovician) brachiopods from the Purmamarca region and the Sierra de Mojotoro, Cordillera Oriental of northwestern Argentina. Geobios 35 (6): 647-661. https://doi.org/10.1016/S0016-6995(02)00079-7

Benedetto, J.L.; Muñoz, D.F. 2017. Plectorthoid brachiopods from the Lower Ordovician of north-western Argentina; phylogenetic relationships with Tarfaya Havlíček and the origin of heterorthids. Journal of Systematic Palaeontology 15 (1): 43-67. https://doi.org/10.1080/14772019.2016.1144086

Benedetto, J.L.; Sánchez, M.T.; Carrera, M.G.; Brussa, E.D.; Salas, M.J. 1999. Paleontológical constraints on successive paleogeographic positions of the Precordillera terrane during the early Paleozoic. In Laurentia-Gondwana connections before Pangea (Ramos, V.A.; Keppie, D.; editors). Geological Society of America, Special Paper 336: 21-42. https://doi.org/10.1130/0-8137-2336-1.21

Bergström, S.M.; Chen, X.; Gutiérrez-Marco, J.C.; Dronov, A. 2009. The new chronostratigraphic classification of the Ordovician System and its relations to major regional series and stages and to δ¹³C chemostratigraphy. Lethaia 42 (1): 97-107. https://doi.org/10.1111/j.1502-3931.2008.00136.x

Buatois, L.A.; Mángano, M.G. 2003. Sedimentary facies and depositional evolution of the Upper Cambrian-Lower Ordovician Santa Rosita Formation in northwest Argentina. Journal of South American Earth Sciences 16 (5): 343-363. https://doi.org/10.1016/S0895-9811(03)00097-X

Buatois, L.A.; Zeballo, F.J.; Albanesi, G.L.; Ortega, G.; Vaccari, E.; Mángano, M.G. 2006. Depositional environments and stratigraphy of the Upper Cambrian-Lower Ordovician Santa Rosita formation at the Alfarcito area, Cordillera Oriental, Argentina: integration of biostratigraphic data within a sequence stratigraphic framework. Latin American Journal of Sedimentology and Basin Analysis 13 (1): 1-29.

Coira, B.; Pérez, B.; Flores, P.; Kay, S.M.; Woll, B.; Hanning, M. 1999. Magmatic sources and tectonic seting of Gondwana margin Ordovician magmas, northern Puna of Argentina and Chile. In Laurentia-Gondwana connections before Pangea (Ramos, V.A.; Keppie, J.D.; editors). Geological Society of America, Special Paper 336: 145-170. https://doi.org/10.1130/0-8137-2336-1.145

Cooper, R.A.; Nowlan, E.S.; Williams, S.H. 2001. Global stratotype section and point for the base of the Ordovician System. Episodes 24 (1): 19-28. http://dx.doi.org/10.18814/epiiugs/2001/v24i1/005

Fernández, R.I. 1985. Bioestratigrafía Cambro-Ordovícica del tramo superior de la Quebrada de Humahuaca, provincia de Jujuy, Argentina. In Congreso Geológico Chileno, No. 4: 284-308. Antofagasta.

Fortey, R.A. 1988. Seeing is believing: gradualism and punctuated equilibria in the fossil record. Science Progress 72 (1): 1-19.

Giuliano, M.E.; Ortega, G.; Albanesi, G.L.; Monaldi, C.R. 2013. Upper Cambrian/Lower Ordovician conodont and graptolite stratigraphic records in the Lari section, Salar del Rincón, Puna of Salta, Argentina. In Conodonts from the Andes (Albanesi, G.L.; Ortega, G.; editors). Asociación Paleontológica Argentina, Publicación Especial 13: 33-37.

Harper, D.A.T.; Villas, E.; Ortega, G. 2004. Lipanorthis Benedetto from the Tremadocian of NW Argentina reidentified as dalmanellidine: Significance for the origin and early radiation of punctate orthide brachiopods. Lethaia 37 (3): 271-279. https://doi.org/10.1080/00241160410006537

Harrington, H.J.; Leanza, A.F. 1957. Ordovician trilobites of Argentina. University of Kansas Press, Department of Geology: 276 p. Lawrence.

Havlíček, V. 1994. Kvania n. g. and Petrocrania Raymond (Brachiopoda, Ordovician) in the Prague basin. Journal of the Czech Geological Society 39 (4): 297-302.

Herrera, Z.A.; Benedetto, J.L. 1991. Early Ordovician brachiopod faunas form the Precordillera basin, western Argentina: biostratigraphy and paleobiogeographical affinities. In Brachiopods through time (MacKinnon, D.I.; Lee, D.E.; Campbell, J.D.; editors). A.A. Balkema: 283-301. Rotterdam.

Hunt, G. 2008. Evolutionary patterns within fossil lineages: Model-based assessment of modes, rates, punctuations and process. In From Evolution to Geobiology: Research questions driving Paleontology at the start of a new century (Kelley, P.H.; Bambach, R.K.; editors). Paleontological Society Papers 14: 117-131.

Isaacson, P.E.; Antelo, B.; Boucot, A.J. 1976. Implications of a Llandovery (Early Silurian) brachiopod fauna from Salta Province, Argentina. Journal of Paleontology 50 (6): 1103-1112.

Jackson, J.B.C.; Cheetham, A.H. 1999. Tempo and mode of speciation in the sea. Trends in Ecology & Evolution 14 (2): 72-77. https://doi.org/10.1016/s0169-5347(98)01504-3

Jin, J. 2001. Early Silurian stricklandiid brachiopod evolution in eastern North America. In Brachiopods: past and present (Brunton; H.; Cocks, L.R.M.; Long, S.L.; editors). Taylor & Francis: 177-188. London.

Laurie, J.R. 1991. Articulate brachiopods from the Ordovician and Lower Silurian of Tasmania. In Australian Ordovician brachiopod studies (Jell, P.A.; editor). Memoirs of the Association Australasian Paleontologists 11: 1-106. Brisbane.

Lavié, F.J.; Benedetto, J.L. 2023. Lower Tremadocian (Ordovician) lingulate brachiopods from the Central Andean Basin (NW Argentina) and their biogeographical links. Bulletin of Geosciences 98 (1): 79-93.

Malanca, S.; Monteros, J.A.; Moya, M.C. 1998. Nuevos datos paleontológicos de la Formación Las Vicuñas (Tremadoc temprano), Puna occidental argentina. In Congreso Argentino de Paleontología y Bioestratigrafía No. 7: p. 90. Bahía Blanca.

Mángano, M.G.; Buatois, L.A. 1999. Ichnofacies models in Early Paleozoic tide-dominated quartzites: Onshore-Offshore gradients and the classic Seilacherian paradigm. Acta Universitatis Carolinae-Geologica 43 (1): 151-154.

Mángano, M.G.; Buatois, L.A. 2004. Reconstructing Early Phanerozoic intertidal ecosystems: ichnology of the Cambrian Campanario Formation in northwest Argentina. Fossils and Strata 51: 17-38. http://dx.doi.org/10.18261/9781405169851-2004-02

McNamara, K.J. 1990. The role of heterochrony in evolutionary trends. In Evolutionary Trends (McNamara, K.J.; editor). Belhaven: 59-74. London.

Miller, J.F.; Ethington, R.L.; Evans, K.R.; Holmer, L.E.; Loch, J.D.; Popov, L.E.; Repetski, J.E.; Ripperdan, R.L.;Taylor, J.F. 2006. Proposed stratotype for the base of the highest Cambrian stage at the first appearance datum of Cordylodus andresi, Lawson Cove section, Utah, USA. Palaeoworld 15 (3-4): 384-405. https://doi.org/10.1016/j.palwor.2006.10.017

Mottequin, B.; Brice, D.; Legrand-Blain, M. 2014. Biostratigraphic significance of brachiopods near the Devonian-Carboniferous boundary. Geological Magazine 151 (2): 216-228. https://doi.org/10.1017/S0016756813000368

Moya, M.C.; Malanca, S.; Hongn, F.D.; Bahlburg, H. 1993. El Tremadoc temprano en la Puna occidental Argentina. In Congreso Geológico Argentino, No. 12 y Congreso de Exploración de Hidrocarburos, No. 2, Actas 2: 20-30. Mendoza.

Moya, M.C.; Malanca, S.; Monteros, J.A.; Albanesi, G.L.; Ortega, G.; Buatois, L. 2003. Late Cambrian-Tremadocian faunas and events from Angosto del Moreno Section, Eastern Cordillera, Argentina. In Ordovician from the Andes (Albanesi, G.L.; Beresi, M.S; Peralta, S.H.; editors). Instituto Superior de Correlación Geológica (Insugeo), Serie de Correlación Geológica 17: 439-444.

Muñoz, D.F.; Benedetto, J.L. 2016. The eoorthid brachiopod Apheoorthina in the Lower Ordovician of NW Argentina and the dispersal pathways along western Gondwana. Acta Palaeontologica Polonica 61(3): 633-644. http://dx.doi.org/10.4202/app.00241.2016

Niemeyer, H. 1989. El complejo ígneo-sedimentario del Cordón de Lila, Región de Antofagasta: significado tectónico. Revista Geológica de Chile 16 (2): 163-181.

North American Commission on Stratigraphic Nomenclature. 2005. North American Stratigraphic Code. AAPG Bulletin 89 (11): 1547-1591. https://doi.org/10.1306/07050504129

Ortega, G.; Albanesi, G.L. 2005. Tremadocian graptolite-conodont biostratigraphy of the South American Gondwana margin (Eastern Cordillera, NW Argentina). Geologica Acta 3 (4): 355-371. https://doi.org/10.1344/105.000001383

Rao, R.I. 1999. Los conodontes Cambro-Ordovícicos de la sierra de Cajas y del Espinazo del Diablo, Cordillera Oriental, República Argentina. Revista Española de Micropaleontología 31 (1): 23-51.

Rao, R.I.; Hünicken, M.A. 1995. Conodont biostratigraphy of the Cambrian-Ordovician boundary in northwestern Argentina. In Ordovician Odyssey (Cooper, J.D.; Droser, M.L; Finney, S.C; editors), Society of Economic Paleontologist and Mineralogists, Pacific Section 77: 125-128. Fullerton, California.

Rao, R.I.; Tortello, M.F. 1998. Tremadoc conodonts and trilobites from the Cardonal Formation, Incamayo Creek, Salta Province, northwestern Argentina. Palaeontologia Polonica 58: 31-45.

Rao, R.I.; Moya, M.C.; Hünicken, M. 2000. Conodontes en la Formación las Vicuñas (Tremadociano temprano), Puna occidental argentina. Ameghiniana, Suplemento Resúmenes 37 (4): 13-14.

Reyes-Abril, J.; Gutiérrez-Marco, J.C.; Villas, E. 2011. Biostratigraphy of the Middle Ordovician Brachiopods from Central Spain. In Ordovician of the World (Gutiérrez-Marco, J.C.; Rábano, I.; García-Bellido, D.; editors). Instituto Geológico y Minero de España: 463-472.

Rubinstein, C.V.; Vaccari, N.E. 2004. Cryptospore assemblages from the Ordovician/Silurian boundary in the Puna region, north-west Argentina. Palaentology 47 (4): 1037-1061. https://doi.org/10.1111/j.0031-0239.2004.00388.x

Sohrabi, A.; Jin, J. 2013. Evolution of the Rhynchotrema-Hiscobeccus lineage: implications for the diversification of the Late Ordovician epicontinental brachiopod fauna of Laurentia. Lethaia 46 (2): 188-210. https://doi.org/10.1111/j.1502-3931.2012.00333.x

Sproat, C.D.; McLeod, J.S.A. 2023. Sympatric speciation driving evolution of Late Ordovician brachiopod Zygospira in eastern North America. Journal of Paleontology 97 (2): 292-317. https://doi.org/10.1017/jpa.2022.102

Such, P.; Buatois, L.A.; Mángano, M.G. 2007. Stratigraphy, depositional environments and ichnology of the Lower Paleozoic in the Azul Pampa area-Jujuy Province. Revista de la Asociación Geológica Argentina 62 (3): 331-344.

Szduy, K.; Hammann, W.; Villas, E. 2001. The Upper Tremadoc fauna from Vogtendorf and the Bavarian Ordovician from Frankenwald (Germany). Senckenbergiana Lethaea 81: 207-261. https://doi.org/10.1007/BF03043300

Tanaka, S.; Takahashi, A. 2013. The biostratigraphic origin of the theory of punctuated equilibria. Proceedings of the CAPE International Workshops, CAPE Studies in Applied Philosophy & Ethics Series, Vol. 1: 111-126.

Terfelt, F.; Bagnoli, G.; Stouge, S. 2012: Re-evaluation of the conodont Iapetognathus and implications for the base of the Ordovician System GSSP. Lethaia 45 (2): 227-237. https://doi.org/10.1111/j.1502-3931.2011.00275.x

Tortello, M.F.; Rao, R.I. 2000. Trilobites y conodontes del Ordovícico temprano del Angosto de Lampazar (provincia de Salta, Argentina). Boletín Geológico y Minero 111 (2-3): 61-84.

Tortello, M.F.; Esteban, S.B. 2003. Trilobites del Cámbrico tardío de la Formación Lampazar (Sierra de Cajas, Jujuy, Argentina). Implicancias bioestratigráficas y paleoambientales. Ameghiniana 40 (3): 323-344.

Tortello, M.F.; Rábano, I.; Rao, R.I.; Aceñolaza, F.G. 1999. Los trilobites de la transición Cámbrico-Ordovícico en la quebrada Amarilla (Sierra de Cajas, Jujuy, Argentina). Boletín Geológico y Minero 110 (5): 3-20.

Tortello, M.F.; Esteban, S.B.; Aceñolaza, G.F. 2002. Trilobites from the base of the Ordovician System in northwestern Argentina. In Aspects of the Ordovician System in Argentina (Aceñolaza, G.F.; editor). Instituto Superior de Correlación Geológica (Insugeo), Serie Correlación Geológica 16: 131-142. Tucumán.

Turner, J.C.M. 1960. Estratigrafía de la Sierra de Santa Victoria y adyacencias. Boletín de la Academia Nacional de Ciencias 41 (2): 163-196. Córdoba.

Vaccari, N.E.; Waisfeld, B.G. 2000. Trilobites Tremadocianos de la Formación Las Vicuñas, Puna occidental, Provincia de Salta, Argentina. In Memorias Congreso Geológico Boliviano, No. 14: 165-169. La Paz.

Vaccari, N.E.; Waisfeld, B.G.; Marengo, L.; Smith, L. 2010. Kainella Walcott, 1925 (Trilobita, Ordovícico Temprano) en el noroeste de Argentina y sur de Bolivia. Importancia Bioestratigráfica. Ameghiniana 47 (3): 293-305.

Vaccari, N.E.; Waisfeld, B.G.; Canelo, H.N.; Smith, L. 2018. Trilobites from the Iscayachi Formation (Upper Cambrian-Lower Ordovician), Cordillera Oriental, South Bolivia. Biostratigraphic implications. In Fósiles y Facies de Bolivia (Suárez Riglos, R.; Dalenz Farjat, A.; Pérez Leyton, M.A.; editors), Yacimientos Petrolíferos Fiscales Bolivianos: 36-58. Santa Cruz de la Sierra.

Vaucher, R.; Vaccari, N.E.; Balseiro, D.; Muñoz, D.F.; Dillinger, A.; Waisfeld, B.G.; Buatois, L.A. 2020. Tectonic controls on late CambrianEarly Ordovician deposition in Cordillera oriental (Northwest Argentina). International Journal of Earth Sciences 109: 1897-1920. https://doi.org/10.1007/s00531-020-01879-9

Villas, E.; Herrera, Z.A. 2004. Revision of the brachiopod Eoorthis grandis Harrington, 1938, from the Lower Ordovician of Northwestern Argentina. Ameghiniana 41 (1): 119-123.

Villas, E.; Herrera, Z.A.; Ortega, G. 2009. Early orthid brachiopods from the Tremadocian (Lower Ordovician) of Northwestern Argentina. Journal of Paleontology 83 (4): 604-613. https://doi.org/10.1666/08-165R.1

Waisfeld, B.G.; Vaccari, N.E.; Chatterton, B.D.E.; Edgecombe, G. 2001. Systematic of Shumardiidae (Trilobita), with new species from the Ordovician of Argentina. Journal of Paleontology 75 (4): 827-859. https://doi.org/10.1666/0022-3360(2001)0752.0.CO;2

Waisfeld, B.G.; Benedetto, J.L.; Toro, B.A.; Voldman, G.G.; Rubinstein, C.V.; Heredia, S.; Assine, M.L.; Vaccari, N.E.; Niemeyer, H. 2023. The Ordovician of southern South America. In A Global Synthesis of the Ordovician System, Part 2 (Servais, T.; Harper, D.A.T.; Lefebvre, B.; Percival, I.G.; editors). The Geological Society of London, Special Publication 533: 133-173. London. https://doi.org/10.1144/SP533-2022-95

Zeballo, F.J.; Albanesi, G.L. 2009. Conodontes cámbricos y Jujuyaspis keideli Kobayashi (Trilobita) en el Miembro Alfarcito de la Formación Santa Rosita, quebrada de Humahuaca, Cordillera Oriental de Jujuy. Ameghiniana 46 (3): 537-556.

Ziegler, A.M. 1966. The Silurian brachiopod Eocoelia hemisphaerica (J. de C. Sowerby) and related species. Palaeontology 9 (4): 523-543.