Large Cretaceous sphenodontian from Patagonia provides insight into lepidosaur evolution in Gondwana

Abstract

Sphenodontian reptiles successfully radiated during Triassic and Jurassic times, but were driven almost to extinction during the Cretaceous period. The sparse Early Cretaceous record of sphenodontians has been interpreted as reflecting the decline of the group in favour of lizards, their suspected ecological successors. However, recent discoveries in Late Cretaceous beds in Patagonia partially modify this interpretation. Numerous skeletons of a new sphenodontian, Priosphenodon avelasi gen. et sp. nov., were collected from a single locality in the Cenomanian-Turonian Candeleros Formation, where it is more abundant than any other tetrapod group recorded in the quarry (for example, Crocodyliformes, Serpentes, Dinosauria and Mammalia). Adult specimens of Priosphenodon reached one metre in length, larger than any previously known terrestrial sphenodontian. Here we propose, using available evidence, that sphenodontians were not a minor component of the Cretaceous terrestrial ecosystems of South America, and that their ecological replacement by squamates was delayed until the early Tertiary. The new discovery helps to bridge the considerable gap in the fossil record (around 120 million years) that separates the Early Cretaceous sphenodontians from their living relatives (Sphenodon).

A sphenodontine (Rhynchocephalia) from the Miocene of New Zealand and palaeobiogeography of the tuatara ( Sphenodon )

“…This material helps to bridge a gap in the rhynchocephalian fossil record of nearly 70 Mya between the Late Pleistocene ( Worthy & Grant-Mackie 2003) and the Late Cretaceous (Apesteguía & Novas 2003;Martinelli & Forasiepi 2004;Apesteguía 2005a,b). It also represents the first direct evidence that a rhynchocephalian was present on New Zealand prior to the Pleistocene.…”

“…Fraser 1988). However, the geographical range of rhynchocephalians seems to contract after the Early Jurassic, first in Laurasia and later in Gondwana (Evans et al 2001, Apesteguía & Novas 2003Apesteguía 2005a;Jones 2006c), possibly as the result of the competition with derived lizards (Saint-Girons 1985;Milner et al 2000) and/or mammals (Gorniak et al 1982;Whiteside 1986;Jones 2006b). …”

Bite‐force performance of the last rhynchocephalian (Lepidosauria:Sphenodon)

“…Available fossil evidence does indicate a change in global lepidosaur communities from those dominated by rhynchocephalians to those dominated by squamates (Evans 1995). The pattern of replacement occurs first in Asia, later in North America, and eventually on the southern continents (Evans et al 2001(Evans et al , 2004Apesteguía & Novas 2003;Jones 2006b). Correspondingly, agamids are not found in New Zealand today, and they are absent from the (admittedly limited) New Zealand fossil record (Milner et al 2000;Mark Hutchinson pers.…”

Predicting the fate of a living fossil: how will global warming affect sex determination and hatching phenology in tuatara?

“…Tuatara earned their status as 'living fossils' due to their morphological similarity to their Mesozoic ancestors (Apesteguía & Novas 2003). Their lineage evolved on the Pangean supercontinent that was characterized by rapid and severe fluctuations in air temperature (Fastovsky & Weishampel 2005), and the survival of tuatara and other basal reptiles (crocodilians and chelonians) suggests that either TSD evolved later or that these reptiles were able to adapt to past climate change.…”