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. 2014 Oct 7;281(1792):20140811.
doi: 10.1098/rspb.2014.0811.

The youngest South American rhynchocephalian, a survivor of the K/Pg extinction

Sebastián Apesteguía  1 , Raúl O Gómez  2 , Guillermo W Rougier  3
Affiliations

The youngest South American rhynchocephalian, a survivor of the K/Pg extinction

Sebastián Apesteguía et al. Proc Biol Sci. .

Abstract

Rhynchocephalian lepidosaurs, though once widespread worldwide, are represented today only by the tuatara (Sphenodon) of New Zealand. After their apparent early Cretaceous extinction in Laurasia, they survived in southern continents. In South America, they are represented by different lineages of Late Cretaceous eupropalinal forms until their disappearance by the Cretaceous/Palaeogene (K/Pg) boundary. We describe here the only unambiguous Palaeogene rhynchocephalian from South America; this new taxon is a younger species of the otherwise Late Cretaceous genus Kawasphenodon. Phylogenetic analysis confirms the allocation of the genus to the clade Opisthodontia. The new form from the Palaeogene of Central Patagonia is much smaller than Kawasphenodon expectatus from the Late Cretaceous of Northern Patagonia. The new species shows that at least one group of rhynchocephalians not related to the extant Sphenodon survived in South America beyond the K/Pg extinction event. Furthermore, it adds to other trans-K/Pg ectotherm tetrapod taxa, suggesting that the end-Cretaceous extinction affected Patagonia more benignly than the Laurasian landmasses.

Keywords: cretaceous/palaeogene boundary; opisthodontia; palaeocene; patagonia; rhynchocephalia.

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Figures

Figure 1.
Figure 1.
Kawasphenodon peligrensis sp. nov. (a–c) Holotype MPEF PV 1989. Left lower jaw in lingual (a), labial (b) and occlusal (c) views. (d–f) Paratype MPEF PV 1990. Right lower jaw in lingual (d), labial (e) and occlusal (f) views. (g) Close-up of additional tooth in occlusal view of MPEF PV 1989. (h) Close-up of additional tooth in occlusal view of MPEF PV 1990. adt, additional teeth; anf, angular facet; mg, meckelian groove; or, ornamentation; pg, posterior groove; sb, secondary bone; st, striae; wf, wear facet. Scale bars: (a–c,d–f) 5 mm; (g,h) 1 mm.
Figure 2.
Figure 2.
(a) Time-tree of rhynchocephalians based on the strict consensus of 22 most parsimonious trees obtained in the phylogenetic analysis, in which the K/Pg boundary is indicated by a dotted line and black silhouettes indicate the relative size of opisthodontian species and a few other eupropalinal rhynchocephalians (see the electronic supplementary material). (b) Palaeogeographic map of the Late Cretaceous (70 Ma; modified from [16]) showing the record of Kawasphenodon (1, K. peligrensis; 2, K. expectatus) and the other certain post-Cretaceous fossil rhynchocephalians (3, Sphenodon or Sphenodon-like records from the Miocene and Quaternary of New Zealand [15]). Afr, Africa; Ant, Antarctica; Aus, Australia; Ind, India; NZ, New Zealand; SAm, South America; E, Early; L, Lower; M, Middle; Maas, Maastrichtian; Plio, Pliocene; Pleis, Pleistocene; Q, Quaternary.
See this image and copyright information in PMC

References

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