New record of snakes from the Cretaceous of Patagonia (Argentina) Adriana María ALBINO CONICET, Departamento de Biología, Universidad Nacional de Mar del Plata, Funes 3250, 7600 Mar del Plata (Argentina) [email protected] Albino A. M. 2000. — New record of snakes from the Cretaceous of Patagonia (Argentina). Geodiversitas 22 (2) : 247-253. KEY WORDS Cretaceous, Serpentes, ABSTRACT Madtsoiidae, New remains of snakes from the Late Cretaceous (La Colonia Formation; ?Boidae, Campanian-Maastrichtian) of Argentina increase the record of the earliest incertae sedis, Patagonia, Patagonian snakes. They include the southernmost record of the madtsoiid paleobiogeography. snake Alamitophis, another probable madtsoiid, perhaps a boid, and a snake incertae sedis. MOTS CLÉS RÉSUMÉ Crétacé, serpents, De nouveaux restes de serpents du Crétacé supérieur de Patagonie (Argentine). Madtsoiidae, De nouveaux restes de serpents du Crétacé supérieur (Formation La Colonia ; ?Boidae, Campanien-Maastrichtien) d’Argentine sont décrits. Ils comprennent le incertae sedis, Patagonie, représentant le plus austral du madtsoiidé Alamitophis, un autre probable paléobiogéographie. madtsoiidé, peut-être un Boidae et un serpent incertae sedis. GEODIVERSITAS • 2000 • 22 (2) © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris. www.mnhn.fr/publication/ 247 Albino A. M. 70° 65° 35° s pa ire La Pam s A s o n e u B Neuquen 4 Río Negro CHILE 3 40° 2 1 Chubut 45° N 45° 0 200 km 75 70° 65° 60° FIG. 1. — Localities. 1, eastern slopes between El Buitre Chico and El Buitre hills, La Colonia area, “Comarca Norpatagónica”. Second facies association of the La Colonia Formation (Campanian-Maastrichtian age); 2, Cerro Cuadrado, Arroyo Verde, middle section of the Los Alamitos Formation (Campanian age, Bonaparte 1996); 3-4, other Late Cretaceous Patagonian localities bearing remains of Alamitophis argentinus; 3, El Palomar; 4, Bajo Trapalcó. INTRODUCTION ince have permitted to recover vertebrate remains from the middle portion of the second facies According to previous records, Cretaceous Pata- association of the La Colonia Formation (Pesce gonian snakes include Dinilysiidae, Madtsoiidae 1979), Campanian-Maastrichtian age (Pascual et and Boidae (Albino 1996). During the last years, al. in prep.). The vertebrates come from the east- expeditions from both the Museo de La Plata ern slopes of the La Colonia area, between El (MLP) and the Museo Paleontológico “Egidio Buitre Chico and El Buitre hills (approximately Feruglio” in Trelew (MPEF) to the southern between 42º55’S, 43º02’S and 67º28’W, slopes of the North Patagonian massif (“Comarca 67º41’W) (Fig. 1). The second facies association Norpatagónica”) in North-central Chubut prov- of the La Colonia Formation is interpreted as 248 GEODIVERSITAS • 2000 • 22 (2) Cretaceous snakes from Patagonia AB CD FIG. 2. — MPEF-PV 643, Alamitophis argentinus, trunk vertebra. A, anterior view; B, posterior view; C, lateral view; D, ventral view. Scale bar: 5 mm. having been deposited in an estuary, tidal flat or to the Eocene (Albino 1996). Their mid-trunk coastal plain environment, influenced both by vertebrae have a unique true derived feature: occasional high fresh water streamflow from the presence of parazygantral foramina. They are also continent and tidal currents from the sea (Pascual characterized by the presence of paracotylar et al. in prep.). Most of the collected vertebrates foramina, the synapophyses located low from the (fishes, turtles, crocodiles, plesiosaurs, dinosaurs, centrum and the absence of prezygapophysial snakes and mammals) come from this second processes (Albino 1996). facies association (Pascual et al. in prep.). The aim of this paper is to describe the first snake Genus Alamitophis Albino, 1986 remains proceeding from that locality. Alamitophis argentinus Albino, 1986 (Fig. 2) SYSTEMATICS MATERIAL EXAMINED. — MPEF-PV 643, trunk vertebra. Order SERPENTES Linnaeus, 1758 Suborder ALETHINOPHIDIA Nopcsa, 1923 REMARKS The specimen is characterized by its small size, Family MADTSOIIDAE Hoffstetter, 1961 high and wide neural arch, high and thick neural spine, thin zygosphene without a median lobe, The monophyletic madtsoiid snakes are recorded parazygantral and paracotylar foramina present, from the Cretaceous to the Pleistocene, but in high neural canal, zygapophyses located at a high South America they have only been recorded up level and inclined above horizontal, prezyga- GEODIVERSITAS • 2000 • 22 (2) 249 Albino A. M. pophysial process absent, moderately elongate of the neural arch are not completely preserved in and anteriorly not widened vertebral centrum, the most complete specimen (MPEF-PV 646). It distinctive haemal keel and large and wide cotyle. is a medium-sized vertebra and it has an elongate and narrow vertebral centrum, wide neural arch, Family ?MADTSOIIDAE large cotyle, thick and narrow zygosphene, left prezygapophysis located at a high level and MATERIAL EXAMINED. — MPEF-PV 641, MPEF- PV 644 and MPEF-PV 645, incomplete vertebrae. inclined above the horizontal, and paracotylar foramina present. It is not possible to see whether REMARKS there is a prezygapophysial process; however, the The parazygantral foramina are not visible in vertebra is rather distinct from all other vertebrae these specimens because the postzygapophyses described in this paper. MPEF-PV 647 is a thick are broken, therefore the remains are tentatively and large zygosphene reminiscent to that of large referred to madtsoiids due to the general consti- boids or madtsoiids. Other remains (MPEF- tution and the absence of prezygapophysial PV 648 and 649) are extremely fragmentary and processes. MPEF-PV 641 is an incomplete verte- tentatively assigned to boid or madtsoiid. bra characterized by its large size, wide neural arch, short and anteriorly widened vertebral cen- Order SERPENTES incertae sedis trum, small neural canal, thick zygosphene, (Fig. 3) prezygapophyses inclined above horizontal, prezygapophysial processes absent, large and MATERIAL EXAMINED. — MPEF-PV 642, trunk vertebra. rounded cotyle, lateral, subcentral and paracoty- lar foramina present, synapophyses located low REMARKS from the centrum, and haemal keel developed. It is a small, narrow, rather depressed and elon- MPEF-PV 645 is a large fragment with the right gated vertebra. It has no marked median notch in prezygapophysis and part of the right postzy- the posterior border of the neural arch. This is a gapophysis. It is attributed to the same taxon as plesiomorphic state in snakes. The roof of the MPEF-PV 641 specimen. Its centrum is wide, neural arch is depressed in posterior view. The short and anteriorly widened, with developed neural spine is long, inclined and posteriorly haemal keel, prezygapophysial process absent and thick. The zygapophysial plane is located at a a very small paracotylar foramen on the right side high level and the prezygapophysial facets are of the large cotyle. Both MPEF-PV 641 and clearly slanting like in primitive snakes. There is MPEF-PV 645 vertebrae are very different to not a true prezygapophysial process (plesiomor- those of other cretaceous madtsoiids of phic state), although there is an expansion under Patagonia. MPEF-PV 644 is a left prezygapoph- the prezygapophysial articular facets and the ver- ysis characterized by the absence of prezy- tebra is wider at that level. The postzygapophyses gapophysial process and the presence of are at a higher level than the prezygapophyses. paracotylar foramen. The thin zygosphene is narrower than the cotyle, it is elevated at a medium level and its roof is not Family ?BOIDAE or MADTSOIIDAE notched. The neural canal is large. The subcen- tral ridges of the vertebral centrum are not well MATERIAL EXAMINED. — MPEF-PV 646, MPEF- PV 647, MPEF-PV 648 and MPEF-PV 649, incom- defined and anteriorly the centrum is not signifi- plete vertebrae. cantly widened. There is not a marked haemal keel. The cotyle is large, wider than high and REMARKS there are no paracotylar foramina. The subcentral These specimens cannot be accurately deter- and lateral foramina are present. The combina- mined due to their fragmentary preservation. tion of characters in the fossil has not been found Zygapophyses, synapophyses and posterior part in any known snake, however, it is not conven- 250 GEODIVERSITAS • 2000 • 22 (2) Cretaceous snakes from Patagonia AB C DE FIG. 3. — MPEF-PV 642, Serpentes incertae sedis, trunk vertebra. A, anterior view; B, posterior view; C, lateral view; D, dorsal view; E, ventral view. Scale bar: 3 mm. ient to designate a new taxon because at the record (Albino 1996) support this opinion. The moment there is a unique preserved vertebra. incertae sedis snake vertebra discovered at the La Colonia Formation (see this paper) corroborates that idea because it has common features with the DISCUSSION most primitive snakes. That indicates that South America played an important role in the early The primitive fossil snake Dinilysia patagonica radiation of snakes. Woodward, 1901 from the Late Cretaceous of According to the record, madtsoiids and boids Patagonia and the distribution of extant primi- were common in the Patagonian Cretaceous- tive alethinophidians in Gondwanan areas sug- Paleogene land communities (Albino 1996). The gest that a great diversity of primitive snakes lived oldest boids in South America come from the in Gondwana (Underwood & Stimson 1990). middle section of the Los Alamitos Formation Earliest distribution of madtsoiids and boids and (Campanian, Bonaparte 1996) in