New data on the Late Cretaceous lizard Dicothodon bajaensis (Squamata, Borioteiioidea) from Baja California, Mexico reveals an unusual tooth replacement pattern in squamates

Abstract

Borioteiioids comprise an extinct family of squamates that inhabited the Northern Hemisphere during the Cretaceous and were characterized by varying patterns of tooth replacement and dental morphology. Understanding the evolution of these tooth replacement patterns has, however, been largely hampered by an extremely fragmentary fossil record. Here we present new information on Dicothodon bajaensisfrom the Campanian of Baja California (Mexico), so far known only from isolated teeth and jaw fragments. Among abundant new materials there are ten maxillae and five dentaries belonging to distinct ontogenetic stages. Whereas juveniles display active tooth replacement, older specimens show no evidence of replacement. Dicothodon bajaensis is therefore inferred to have had arrested tooth replacement later in ontogeny. This provides the first evidence of cessation of tooth replacement during late ontogeny in lizards (living or extinct). This replacement type is also an evolutionary intermediate between the typical lizard replacement pattern, observed in some borioteiioids (e.g., Bicuspidon) and the complete absence of tooth replacement since early ontogeny as observed in other borioteiioids (e.g., Polyglyphanodon).

A tiny new Middle Triassic stem-lepidosauromorph from Germany: implications for the early evolution of lepidosauromorphs and the Vellberg fauna

“…Cases of even partial development of the acrodont condition are extremely rare in non-lepidosauromorph reptiles 33 , such as in the captorhinid Opisthodontosaurus 32 . However, the evolution of acrodonty or pleuroacrodonty (respectively, total or partial placement of the dental tissue on the apex of the jawbone) has occurred at least five independent times in lepidosauromorphs: in sphenodontians, priscagamids, acrodontans, borioteiioids, and trogonophid amphisbaenians [33][34][35][36] . Vellbergia thus demonstrates that this important dental character, which is conspicuous and diagnostic for some lepidosaur lineages (e.g.…”

Assessing ontogenetic maturity in extinct saurian reptiles

“…3; Reynoso, 1996, 1997, 2003; Rieppel, 1992 c ; de Vivar Martínez & Soares, 2015; O'Brian, Whiteside & Marshall, 2018; Hsiou et al ., 2019). By contrast, there is only one use of teeth to assess maturity in squamates in our database: in the Cretaceous lizard Dicothodon bajaensis addition of teeth to the tooth row posteriorly, and ankylosis of the posteriormost tooth (Chavarría‐Arellano, Simões & Montellano‐Ballesteros, 2018). Heterodonty has been suggested to increase during ontogeny in heterodont lizards (Edmund, 1969), but to our knowledge this has not been used to assess maturity in squamates.…”

A new toothless pterosaur (Pterodactyloidea) from Southern Brazil with insights into the paleoecology of a Cretaceous desert

“…An acrodont lizard, Gueragama sulamericana Simões et al 2015, which was described based on fragmentary material (Simões et al 2015), complete the known reptilian fauna from this site. Lizard remains tend to be quite incomplete (e.g., Chavarría-Arellano et al 2018), for all those representing ancient desertic environments.…”