Hsiou & Albino, 2010-Viperidae Pleistocene Brazilian Amazonia

Hsiou & Albino, 2010-Viperidae Pleistocene Brazilian Amazonia

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First record of Viperidae snakes from the Pleistocene of southwestern

Brazilian Amazonia Annie S. Hsioua; Adriana M. Albinob a °Seção de Paleontologia, Museu de Ciências Naturais, Rio Grande do Sul, Brazil b CONICET, Departamento de Biología, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina

First published on: 02 December 2010

To cite this Article Hsiou, Annie S. and Albino, Adriana M.(2010) 'First record of Viperidae snakes from the Pleistocene of southwestern Brazilian Amazonia', Alcheringa: An Australasian Journal of Palaeontology,, First published on: 02 December 2010 (iFirst)

To link to this Article: DOI: 10.1080/03115518.2011.519646 URL: http://dx.doi.org/10.1080/03115518.2011.519646

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First record of Viperidae snakes from the Pleistocene of southwestern Brazilian Amazonia

HSIOU, A.S. & ALBINO,A .M. iFirst article. First record of Viperidae snakes from the Pleistocene of southwestern Brazilian Amazonia. Alcheringa, 1–7. ISSN 0311–5518.

We describe an incomplete trunk vertebra of a snake attributable to the Viperidae, collected from a conglomerate facies in upper Pleistocene sediments at the Mississippi locality, Upper Jurua River, southwestern Brazilian Amazonia. It represents the first fossil snake record from the Pleistocene of this region. This specimen extends the fossil distribution of the Viperidae, representing the northernmost record of a snake in the Brazilian Pleistocene.

Annie S. Hsiou [anniehsiou@gmail.com], 8Secao de Paleontologia, Museu de Ciencias Naturais, FZB-RS, Av. Salvador Franca, 1427, CEP: 90690-0, Jardim Botanico, Porto Alegre, Rio Grande do Sul, Brazil; Adriana M. Albino [aalbino@mdp.edu.ar], CONICET, Departamento de Biologıa, Universidad Nacional de Mar del Plata, Funes 3250, 7600 Mar del Plata, Argentina. Received 4.5.2010; revised 26.7.2010; accepted 6.8.2010.

Key words: Viperidae, Pleistocene, Brazil, Amazonia.

PLEISTOCENE vertebrates from southwestern Brazilian Amazonia occur in several localities together with Neogene fossils because Pleistocene terraces developed on older Cenozoic sediments that were bisected by the same rivers that produced these terraces (Latrubesse & Rancy 1998, Cozzuol 2006). The Pleistocene vertebrate fauna at these localities includes mainly fossil mammals, represented by carnivores, notoungulates, xenarthrans, proboscideans, sirenians, perissodactyles and artiodactyles (Simpson & Paula-Couto 1981, Ranzi 2000, 2008). Two fossiliferous units can be found along the Upper Jurua River of Acre State (Latrubesse & Rancy 1998). The older Solimo es Formation contains a Miocene vertebrate fauna (see Cozzuol 2006). Younger (late Pleistocene) bone-bearing conglomerates, as defined by Simpson & Paula-Couto (1981), are exposed unconformably over this unit. The snake vertebra described here (LPVCZS/001) was collected in the late Pleistocene conglomerate facies at the Mississippi locality (probably ‘Estira od oM ississippi’, locality 1, ‘Pernambuquinho’ locality of Simpson & Paula-Couto 1981), near the municipality of Marechal Taumaturgo, Acre State, Brazil (Fig. 1). Here we describe the fossil vertebra, which to date represents a unique specimen of Viperidae snakes for the Pleistocene of southwestern Brazilian Amazonia.

Material and methods

Skeletons of extant and fossil snakes were used for comparisons (Appendix). Osteological terms, measurements and systematic hierarchy follow Auffenberg (1963), Hoffstetter & Gasc (1969), Rage (1984), Zaher (1999) and Holman (2000).

Vertebral measurements: cl, centrum length; coh, condyle height; cow, condyle width; cth, cotyle height; ctw, cotyle width; naw, neural arch width at interzygapophy-

ISSN 0311-5518 (print)/ISSN 1752-0754 (online) 2010 Association of Australasian Palaeontologists DOI: 10.1080/03115518.2011.519646

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seal ridge; nch, neural canal height; ncw, neural canal width; po–po, distance between postzygapophyses; pr–pr, distance between prezygapophyses; pr–po, distance between pre- and postzygapophyses of the same side; prl, prezygapophysis length; prw, prezygapophysis width; zh, zygosphene height; zw, zygosphene width.

Institutional abbreviations. LPV/CZS,

Colec a o de Vertebrados do Laborato rio de Paleontologia, Centro Multidisciplinar, Universidade Federal do Acre/Campus Floresta, Cruzeiro do Sul, Brazil; MCN.D., Colec a o Dida tica de Herpetologia, Museu de Cie ncias Naturais da Fundac a o Zoobota nica do Rio Grande do Sul, Porto Alegre, Brazil; MCP-AN, Colec a o de Herpetologia, Anexos, Museu de Cie ncias e Tecnologia da Pontifıcia Universidade Cato lica do Rio Grande do Sul (PUCRS), Porto Alegre, Brazil.

Systematic palaeontology

OPHIDIA Brongniart, 1800 ALETHINOPHIDIA Nopcsa, 1923 CAENOPHIDIA Hoffstetter, 1939 COLUBROIDEA Oppel, 1811 VIPERIDAE Oppel, 1811

Indeterminate genus and species (Fig. 2).

Referred specimen. One incomplete trunk vertebra, LPVCZS/001.

Locality, unit and age. Mississippi locality (08856033.400S, 72845049.400W) (probably locality 1, ‘Pernambuquinho’ or ‘Estira od o Mississippi’ of Simpson & Paula-Couto 1981), Upper Jurua River, Acre State; river terrace sediments; late Pleistocene.

Description. This vertebra has lost most of the neural spine and the distal

Fig. 1. Map of southwestern Brazilian Amazonia, Acre State, Brazil, showing the fossil locality ‘Mississippi’.

2 ANNIE S. HSIOU and ADRIANA M. ALBINO ALCHERINGA

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part of the hypapophysis. Overall, the vertebra is relatively large (Fig. 2A–E), wider than long (pr–pr4pr–po), with an elongate centrum that is longer than the width of the neural arch (cl/ naw41).

Fig. 2. Viperidae indeterminate genus and species. Photographs of a midtrunk vertebra, from the late Pleistocene of southwestern Brazilian Amazonia (Mississippi locality, Upper Jurua River), LPVCZS/001, in (A) anterior, (B) posterior, (C) lateral, (D) dorsal and (E) ventral views. Scale bar¼5 m.

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In anterior view, the zygosphene is thin and shows a straight dorsal margin, with smalland dorsally angled articular facets. The prezygapophyses are slender, long and slightly oblique in relation to the horizontal plane. The prezygapophyseal process is small and robust.The neural canal is subtriangular, low and wide. The cotyle is nearly circular (ctw*cth) and narrower than the zygosphene (ctw5zw). The paradiapophyses are well developed, with a prominent and spherical diapophysis, posterodorsally inclined, hardly distinctfrom a large and concave parapophysis. A well-developed and slightly inclined parapophyseal process projects anteroventrally and extends clearly beyond the ventral rim of the cotyle. One pair of small paracotylar foramina are evident, one foramen is located on each side of the cotyle, placed in a deep depression.

In posterior view, the roof of the neural arch is moderately depressedand bearsa deep posterodorsal notch. The postzygapophyses are elongated and slightly inclined dorsolaterally. The zygantra are large and deep, with a small foramen within each zygantrum. The condyle is nearly circular. Ventral to the condyle, the hypapophysis is very prominent and, although broken, it clearly surpasses the ventral rim of the condyle.

In lateral view, the neural spine is relatively well developed, probably high, and considerably elongated anteroposteriorly. In this view, the paradiapophyses are clearly oriented dorsoventrally as a whole. The diapophysial and parapophysial surfaces are very distinct from each other. Anteroventral to the parapophyses, a prominent and spatulate parapophyseal process projects strongly forwards. Small lateral foramina aree vident on thes idew alls of then eural arch, more or less positioned at the diapophysial level. The elongate centrum carries a robust and prominent hypapophysis, ventroposteriorly positioned. The distal portion of the hypapophysis is lost, but it surpasses clearly the ventral margin of the condyle.The centrum is delimited by anteriorly welldefined subcentral ridges that vanish in the posteriorh alfo ft he centrum.

In dorsal view, the neural arch is wider than long (pr–pr4pr–po). The posterodorsal notch of the neural arch is distinct, and the broad and robust base of the neural spine extends upwards and backwards from the base of the zygosphene. The articular facets of the prezygapophyses are slender, longer than broad (prl4prw), with the main axis rather laterally orientated. A small prezygapophyseal process projects slightly beyond the articular facets of the prezygapophysis. The interzygapophyseal constriction is long and distinct in the middle. The anterior margin of the zygosphene is almost straight, with articular facets rather anteriorly orientated. The neural spine has a thin base, becoming wider posteriorly.

In ventral view, the centrum is narrow and elongate. The subcentral grooves are of slight depth but well delimited anteriorly. The hypapophysis is prominent and ventroposteriorly inclined. Small subcentral foramina are situated anterolaterally, close to the hypapophysis. The subcentral ridges are visible, extending from the ventral face of the diapophysis. They disappear abruptly more or less reaching the middle portion of the centrum. The precondylar constriction is moderately marked.

Comments. With regard to the overall morphology of the vertebra, LPVCZS/001 exhibits the following combination of characters present in viperids: vertebra not strongly elongate; a low and wide neural canal; subcentral ridges only on anterior portion of centrum; width of hypapophysis more than one-third the width of the

4 ANNIE S. HSIOU and ADRIANA M. ALBINO ALCHERINGA Downloaded By: [Hsiou, Annie] At: 12:45 2 December 2010 condyle; cotyle and condyle large; neural arch wide and depressed; and prezygapophyseal processes short (see Auffenberg 1963, Rage 1984, Szyndlar 1984, Holman 2000, Albino & Montalvo 2006, Head et al. 2006). The vertebra LPVCZS/001 also has a well-developed and strongly anteroventrally oriented parapophyseal process (Zaher 1999). Although this condition is proposed as a synapomorphy of viperids (Zaher 1999), it is also observed in natricine ‘colubrids’ although less well developed (Auffenberg 1963, Zaher 1999). The natricines have a laterally compressed hypapophysis that extends further anteriorly along the centrum as a keel (Parmley & Walker 2003, Albino & Montalvo 2006). Both in the fossil specimen and in the available specimens of the extant viperids Crotalus and Bothrops, the hypapophysis is thick, more ventrally directed and does not extend anteriorly. In addition, the fossil specimen shows the condyle poorly separated from the hypapophysis base; this feature could be diagnostic of viperid snakes (Rage pers. comm. in Albino & Montalvo 2006).

Currently, there are five genera (Bothriopsis, Bothrocophias, Bothrops, Crotalus and Lachesis) and 30 species of Viperidae recognized in Brazil (Melgarejo 2003). Among them, only Bothriopsis, Bothrops and Lachesis inhabit the Acre region of southwestern Brazilian Amazonia (Silva 2006, unpublished data). According to Albino & Montalvo (2006) there are no known vertebral synapomorphies that can be used to differentiate viperid genera and species, and isolated fossil vertebrae are assigned to genera and species based on combinations of characters of uncertain polarities. Bothrops has large or small paracotylar foramina (Albino & Montalvo 2006, pers. obs.), whereas in Crotalus these foramina are small (Auffenberg 1963, Holman 2000, pers. obs.). The fossil specimen has small paracotylar foramina, which is consistent with the morphology of both genera. Camolez (2006, unpublished data) identified some subtle differences in vertebral morphology between Bothrops and Crotalus. These differences are based mainly on the neural spine, which is not preserved in the fossil material. The parapophyseal processes of both genera are also slightly distinct. In Bothrops, the parapophyseal process is divergent and laterally oriented, whereas Crotalus has a more strongly developed parapophyseal process that is parallel and anteriorly inclined. Another differentiating feature is that Crotalus has a subtle to strong V-shaped anterior of the zygosphene, whereas Bothrops has an anterior rectilinear or convex edge (Camolez 2006, unpublished data). The fossil specimen shares the parapohyseal process and zygosphene morphology with Bothrops; thus, it has closer affinities with this genus than with Crotalus. Nevertheless, due to the absence of vertebral columns of the other Brazilian viperid genera available in institutional collections for comparison, the generic assigment of the specimen remains uncertain.

Conclusions

The described fossil vertebra is the first record of snakes for the late Pleistocene of southwestern Brazilian Amazonia. The presence of a viperid in the Pleistocene of Brazil accords with the oldest record of the lineage in the Miocene of South America (Albino 1989, Albino & Montalvo 2006). The Brazilian record of Colubroidea is represented by isolated vertebrae from the late Pleistocene–Holocene of the southwest, central-west and northeastern regions. All previously identified fossil specimens are assigned to extant Brazilian snake genera among the ‘colubrids’, viperids (Bothrops and Crotalus) and elapids (Micrurus) (Camolez 2006, unpublished data). Recently, Hsiou et al. (2009) reported some fossil vertebrae of colubroid snakes from the Quaternary of the Provıncia Espeleolo gica

ALCHERINGA VIPERID SNAKE FROM BRAZIL 5 Downloaded By: [Hsiou, Annie] At: 12:45 2 December 2010 de Ubajara, Ceara State, northeastern Brazil. They include indeterminate ‘colubrids’ and a form attributable to the Viperidae (Crotalus). This colubroid record of Brazil, together with the well-supported Miocene– Pleistocene record of Argentina (Albino 1989, 1995, 1996a, b, 1999, Albino & Quintana 1992, Albino & Montalvo 2006) and Pleistocene record of Venezuela (Head et al. 2006), suggest that some elements of the South American snake fauna have been well established since the Pleistocene. The fossil reported in this paper extends the past distribution of the family Viperidae, representing the northernmost record of a snake in the Brazilian Pleistocene.

Acknowledgements

The authors thank CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnolo gico) for financial support to ASH for research at Universidade Federal do Rio Grande do Sul (PPGGeocie ncias/UFRGS). Thanks are also due to K.A. Rodrigues (UFAC/Cruzeiro do Sul) for the loan of fossil snake material; to M.L. Arau jo, M.L.M. Alves (MCN/FZBRS) and G.F. Pontes (MCT-PUCRS) for the loan or donation of the colubroid specimens; and to J.C. Cisneros (UFPI) and M. Santos (UFRGS) for English revision of the manuscript. We also thank Dr Stephen McLoughlin, Editor in Chief, and two anonymous reviewers for their constructive comments.

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