A Review of Vertebrate Beak Morphologies in the Triassic; A Framework to Characterize an Enigmatic Beak from the Ischigualasto Formation, San Juan, Argentina

Wynd, Brenen M.; Martínez, Ricardo N.; Colombi, Carina E.; Alcober, Oscar A.

doi:10.5710/amgh.13.05.2020.3313

Cited by 4 publications

(2 citation statements)

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“…Recent phylogenetic analyses based on molecular characters suggest that non-avian dinosaurs are deeply phylogenetically nested between the Chelonia, Crocodilia, and Aves (Schweitzer et al, 2009;Chiari et al, 2012;Crawford et al, 2015) so extant phylogenetic bracketing would support the absence of lips as the most likely condition at the root of the dinosaurian clade (Carr et al, 2017). Taking extinct taxa into account, the repeated evolution of a cornified beak among Archelosauria (e.g., in Chelonia, Pterosauria, Ornithischia, many non-avian Theropoda, and Aves) (Norell et al, 2001;Lautenschlager et al, 2013;Wynd et al, 2020) makes the presence of functionally important, non-redundant facial soft tissue an unlikely plesiomorphic state for this clade. All living reptilian species with lips belong to the Lepidosauria (Soares, 2002;Paul, 2018), thus suggesting that phylogenetic effects have to be taken into account while discussing the evolution of lips amongst Sauropsida.…”

Section: The Question Of Lips In Non-avian Theropodsmentioning

confidence: 99%

The rostral neurovascular system of Tyrannosaurus rex

Bouabdellah¹,

Lessner²,

Benoît³

2022

Palaeontol Electron

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The study of the rostral neurovascular system using CT scanning has shed new light on phylogenetic and palaeobiological reconstructions of many extinct tetrapods. This research shows a detailed description of the rostral neurovascular canals of Tyrannosaurus rex including the nasal, maxillary (dorsal alveolar), and mandibular (ventral alveolar) canals. Extensive comparisons with published descriptions show that the pattern of these canals in Tyrannosaurus is not unusual for a non-avian theropod. As in the non-avian theropod Neovenator, the maxillary canal shows several anastomoses of its branches. Differences from the plesiomorphic sauropsid condition are concentrated within the canal for the maxillary neurovasculature, which is primitively horizontal, tubular, and connected to a single row of supralabial foramina, whereas in Tyrannosaurus the main trunk of the canal is oriented more obliquely and dorsally displaced to give room to the deep tooth alveolae. As a result, the lateral branches that provide innervation and blood supply to the skin are dorsoventrally elongated compared to non-theropod taxa, and multiple rows of supralabial foramina are present. An overview of the literature suggests that the evolution of the trigeminal canals among sauropsids only weakly supports previous hypotheses of crocodile-like facial sensitivity in non-avian theropods (except, maybe, in semiaquatic taxa). More systematic studies of the rostral neurovascular canals in non-avian theropods may help answer the question of whether lips were present or not.

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Section: The Question Of Lips In Non-avian Theropodsmentioning

confidence: 99%

The rostral neurovascular system of Tyrannosaurus rex

Bouabdellah¹,

Lessner²,

Benoît³

2022

Palaeontol Electron

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“…Abbreviations: A, Aetosaurinae; D, Desmatosuchini; S, Stagonolepididae; St, Stagonolepidoidea; T, Typothoracinae. tary; see, e.g., Parrish, 1994;Holliday and Nesbitt, 2013;Wynd et al, 2020), it seems to have been absent in N. engaeus (Desojo, 2005;Desojo and Báez, 2007). Most non-aetosaurine aetosaurs lack a tall, thorn-like dorsal process on the articular (Figure 23I), which may have provided additional attachment sites for the M. depressor mandibulae (sensu Desojo and Vizcaíno, 2009), thus revealing further disparity of retroarticular process shape of aetosaurs (Figure 23I).…”

Section: Aetosaur Diet and Paleobiologymentioning

confidence: 99%

Skull osteology of Aetosauroides scagliai Casamiquela, 1960 (Archosauria: Aetosauria) from the Late Triassic of Brazil: New insights into the paleobiology of aetosaurs

Neto

Desojo²,

Brust³

et al. 2021

Palaeontol Electron

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Aetosauroides scagliai, from the Ischigualasto Formation of Argentina and Santa Maria Supersequence of Brazil (Carnian-Norian), is one of the oldest members of Aetosauria, a diverse clade of armored crocodile-line archosaurs. Aetosauroides scagliai differs from other aetosaurs in having the maxilla excluded from the margin of the external nares, the length/width ratio of the postzygapophyses ≤ 0.75, and other features that place it as one of the earliest-diverging members of the clade. In this paper we provide a detailed description of the skull of A. scagliai based on a new Brazilian specimen, revealing that it lacks a pneumatic cavity on the medial surface of the maxilla and further differs from all other known aetosaurs by the presence of ≥ 12 dentary teeth. However, contra previous studies, the elongated posterior process of the jugal does articulate ventrally with the quadratojugal in A. scagliai, forming the posteroventral corner of the skull as in all other aetosaurs. Aetosauroides scagliai exhibits some characters typical of predatory archosaurs (like the recurved ziphodont teeth and mandibular articulation at the level of the tooth row), but was probably an omnivore, as it also shares several probable adaptations for herbivory with aetosaurs generally (i.e., edentulous anterior premaxilla and dentary) and stagonolepidoids specifically (e.g., shovel-shaped snout). This suggests that there was greater trophic diversity in this clade than usually recognized, at least early in their evolutionary history.

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