A new aetosaur (Archosauria, Suchia) from the Upper Triassic Pekin Formation, Deep River Basin, North Carolina, U.S.A., and its implications for early aetosaur evolution

Heckert, Andrew B.; Schneider, Vincent P.; Fraser, Nicholas C.; Webb, R. A.

doi:10.1080/02724634.2014.881831

Cited by 17 publications

(85 citation statements)

References 33 publications

(19 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…() recovered Aetobarbakinoides brasiliensis as the sister taxon of the clade Desmatosuchinae + Typothoracinae, recent analyses (Heckert et al . ; Parker ) have pruned this taxon from the final published tree due to its high instability.…”

Section: Discussionmentioning

confidence: 99%

Novel data on aetosaur (Archosauria, Pseudosuchia) osteoderm microanatomy and histology: palaeobiological implications

Cerda

Desojo

Scheyer³

2018

Palaeontology

View full text Add to dashboard Cite

One of the most striking features of aetosaurs is the possession of an extensive bony armour composed of dorsal, ventral and appendicular osteoderms. With the purpose of establishing the main histological changes during ontogeny and the degree of histological variation within the armour, we analysed the bone histology of dorsal (paramedian and lateral), ventral and appendicular osteoderms from different taxa from the Late Triassic of South America, including Aetosauroides scagliai, Aetobarbakinoides brasiliensis and Neoaetosauroides engaeus. Histological data support an intramembranous origin for osteoderms. Nevertheless, evidence for metaplastic ossification (i.e. structural fibres) at advanced ontogenetic stages, in at least some elements, is also present. A variant type of parallel fibred bone, which we have named ‘crossed parallel fibred bone’, is characterized for aetosaurs. In this pseudosuchian group, osteoderms exhibit very important microstructural changes during ontogeny, which can be useful for determining ontogenetic stages from isolated elements. Histological data suggest a relatively early onset of sexual maturity among aetosaurs. Microanatomical analysis from different taxa reveal that having high values of compactness is the plesiomorphic condition for Aetosauria. The notably increased compactness of the osteoderms does not appear to be related to size, ontogeny, sex or reproductive status of the individuals. Although a high degree of compactness of osteoderms and other bones has been considered as evidence for an aquatic lifestyle in vertebrates, such an inference contradicts the current concept of a fully terrestrial lifestyle in aetosaurs.

show abstract

Section: Discussionmentioning

confidence: 99%

Novel data on aetosaur (Archosauria, Pseudosuchia) osteoderm microanatomy and histology: palaeobiological implications

Cerda

Desojo

Scheyer³

2018

Palaeontology

View full text Add to dashboard Cite

show abstract

“…All fossil material of C. chathamensis , including the holotype specimen and referred materials from the holotype locality (NCPALEO 1902), are housed at NCSM in the vertebrate paleontology collections. These specimens were all collected from a stratigraphically narrow (~30 m thick) layer within the Upper Triassic Pekin Formation of the Chatham Group, Newark Supergroup, North Carolina (Heckert et al, , ). These are among the stratigraphically lowest Upper Triassic aetosaurs from North America (Whiteside et al, ; Heckert et al, ).…”

Section: Methodsmentioning

confidence: 99%

Disparate Growth Strategies within Aetosauria: Novel Histologic Data from the Aetosaur Coahomasuchus chathamensis

Hoffman

Heckert

Zanno

2018

The Anatomical Record

Self Cite

View full text Add to dashboard Cite

Aetosaurs comprise a clade of quadrupedal, armored, omnivores to herbivores that lived across much of the supercontinent of Pangea during the Late Triassic. Their relative abundance in many units, and the rarity of other Triassic herbivores, points to them as key components of Late Triassic ecosystems. Debate persists about whether they were growing more or less slowly when compared to extant crocodylians, and bone histology is sparsely sampled within the group. We undertook a histological examination of Coahomasuchus chathamensis to address its ontogenetic trajectory and characterize its histology. We sampled a paramedian osteoderm from the holotype specimen, as well as five osteoderms (two paramedian, one lateral, and two of uncertain position) and two incomplete limb bones (radius and fibula), from referred specimens discovered at the type locality. Using these we estimated specimen ages with lines of arrested growth (LAGs) to determine that the study individuals reached from 2 to 7 years old. All of the sampled elements contained woven-fibered bone with extensive vasculature within the internal cortex. In some specimens, more poorly vascularized, parallel-fibered bone is evident externally. The holotype of C. chathamensis represents a juvenile individual, and raises the possibility that the holotype of C. kahleorum is a juvenile as well, complicating aetosaur systematics and diversity. When compared to aetosaurs of similar size, it is clear that C. chathamensis was growing comparatively rapidly, about 3 times the rate of similarly sized specimens of Aetosauroides scagliai from Argentina. This discovery reveals the presence of disparate growth strategies within Aetosauria. Anat Rec, 302:1504-

show abstract

“…When Long & Ballew (1985) first proposed a taxonomy of North American aetosaurs based exclusively on osteoderm characters, they recognized only four taxa ( Desmatosuchus , Typothorax , Calyptosuchus , Paratypothorax ). Much new work based upon many new specimens reveals that the particular osteoderm character combinations proposed by Long & Ballew (1985) in fact can occur in many other unique combinations, resulting in the establishment of many new taxa from North America based almost solely on osteoderms (e.g., Zeigler, Heckert & Lucas, 2003 ; Martz & Small, 2006 ; Spielmann et al, 2006 ; Lucas, Hunt & Spielmann, 2007 ; Parker, Stocker & Irmis, 2008 ; Heckert et al, 2015 ). Moreover, it has been demonstrated that aetosaurs with nearly identical osteoderm character combinations can differ significantly in the other portions of the skeleton, especially in the cranial elements, indicating even more taxonomic potential ( Desojo, 2005 ; Desojo & Báez, 2005 ; Desojo & Báez, 2007 ; Desojo & Ezcurra, 2011 ).…”

Section: Introductionmentioning

confidence: 99%

“…Although early studies did focus on character change across broadly defined carapace regions such as the cervical and caudal regions (e.g., Long & Ballew, 1985 ; Heckert & Lucas, 1999 ), more recent studies have sought to detail variation within those subregions ( Martz, 2002 ; Parker, 2003 ; Parker, 2008b ; Schoch, 2007 ; Parker & Martz, 2010 ; Heckert et al, 2015 ). Potentially further complicating this situation is our general lack of data regarding character transformations affected by ontogenetic variation as well as differences caused by individual and sexual dimorphism ( Taborda, Cerda & Desojo, 2013 ; Taborda, Heckert & Desojo, 2015 ).…”

Section: Introductionmentioning

confidence: 99%

“…Potentially further complicating this situation is our general lack of data regarding character transformations affected by ontogenetic variation as well as differences caused by individual and sexual dimorphism ( Taborda, Cerda & Desojo, 2013 ; Taborda, Heckert & Desojo, 2015 ). Overall though, the rich source of character data present in aetosaurian osteoderms provides the systematist with a broad canvas on which to construct a detailed phylogenetic hypothesis, presuming of course that the changes in osteoderm characters are indeed phylogenetically informative ( Parker, 2007 ) and that the homology of these characters can be determined (e.g., Harris, Gower & Wilkinson, 2003 ; Parker & Martz, 2010 ; Heckert et al, 2015 ).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Revised phylogenetic analysis of the Aetosauria (Archosauria: Pseudosuchia); assessing the effects of incongruent morphological character sets

Parker

2016

PeerJ

207

View full text Add to dashboard Cite

Aetosauria is an early-diverging clade of pseudosuchians (crocodile-line archosaurs) that had a global distribution and high species diversity as a key component of various Late Triassic terrestrial faunas. It is one of only two Late Triassic clades of large herbivorous archosaurs, and thus served a critical ecological role. Nonetheless, aetosaur phylogenetic relationships are still poorly understood, owing to an overreliance on osteoderm characters, which are often poorly constructed and suspected to be highly homoplastic. A new phylogenetic analysis of the Aetosauria, comprising 27 taxa and 83 characters, includes more than 40 new characters that focus on better sampling the cranial and endoskeletal regions, and represents the most comprenhensive phylogeny of the clade to date. Parsimony analysis recovered three most parsimonious trees; the strict consensus of these trees finds an Aetosauria that is divided into two main clades: Desmatosuchia, which includes the Desmatosuchinae and the Stagonolepidinae, and Aetosaurinae, which includes the Typothoracinae. As defined Desmatosuchinae now contains Neoaetosauroides engaeus and several taxa that were previously referred to the genus Stagonolepis, and a new clade, Desmatosuchini, is erected for taxa more closely related to Desmatosuchus. Overall support for some clades is still weak, and Partitioned Bremer Support (PBS) is applied for the first time to a strictly morphological dataset demonstrating that this weak support is in part because of conflict in the phylogenetic signals of cranial versus postcranial characters. PBS helps identify homoplasy among characters from various body regions, presumably the result of convergent evolution within discrete anatomical modules. It is likely that at least some of this character conflict results from different body regions evolving at different rates, which may have been under different selective pressures.

show abstract

A new aetosaur (Archosauria, Suchia) from the Upper Triassic Pekin Formation, Deep River Basin, North Carolina, U.S.A., and its implications for early aetosaur evolution

Cited by 17 publications

References 33 publications

Novel data on aetosaur (Archosauria, Pseudosuchia) osteoderm microanatomy and histology: palaeobiological implications

Novel data on aetosaur (Archosauria, Pseudosuchia) osteoderm microanatomy and histology: palaeobiological implications

Disparate Growth Strategies within Aetosauria: Novel Histologic Data from the Aetosaur Coahomasuchus chathamensis

Revised phylogenetic analysis of the Aetosauria (Archosauria: Pseudosuchia); assessing the effects of incongruent morphological character sets

Contact Info

Product

Resources

About