The mystery of Mystriosaurus: redescribing the poorly known Early Jurassic teleosauroid thalattosuchians Mystriosaurus laurillardi and Steneosaurus brevior

Sachs, Sven; Johnson, Michela M.; Young, Mark T.; Abel, Pascal

doi:10.4202/app.00557.2018

Cited by 16 publications

(28 citation statements)

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“…The above analyses, similar to recent studies (Ősi et al, 2018;Foffa et al, 2019;Sachs et al, 2019a), find many aspects of the phylogeny to be consistent, including:…”

Section: Areas Of Uncertaintysupporting

confidence: 84%

“…Thus, the results (12 MPTs with 1666 steps) ( Fig. 1E) were drastically different than those found in Wilberg (2015b), Young et al (2016), Ristevski et al (2018), Ősi et al (2018), Foffa et al (2019), and Sachs et al (2019a).…”

Section: Introductioncontrasting

confidence: 63%

“…in Deslongchampsina) oriented. However, in Mystriosaurus, the external nares are directed anteriorly (Sachs et al, 2019a). This is intriguing, as this positioning would not be practical for a semi-aquatic lifestyle.…”

Section: Palaeoenvironment and The Importance Of Freshwater Teleosaurmentioning

confidence: 99%

“…and Teleosauroidea indeterminate specimens were examined. Overall, approximately 550 teleosauroid specimens were personally studied by MM Johnson. The complete list of 502 characters are presented the Supplemental Material SD1, similar to Ősi et al (2018), Foffa et al (2019), and Sachs et al (2019aSachs et al ( , 2019b. Newly added characters are represented by (NEW), ordered characters are specified by (ORDERED), and characters that cannot be scored (e.g.…”

Section: Character Sampling and Scoringmentioning

confidence: 99%

“…While teleosauroid skeletal and dental morphology has been well documented from the 18th Century to present ( Chapman, 1758 ; Cuvier, 1824 ; Von Meyer, 1837 ; Eudes-Deslongchamps, 1867 ; Blake, 1876 ; Andrews, 1909 , 1913 ; Westphal, 1961 , 1962 ; Young et al, 2014 ; Johnson et al, 2017 ; Johnson, Young & Brusatte, 2019 ; Foffa et al, 2019 ; Sachs et al, 2019a ), the evolutionary relationships of these crocodylomorphs are poorly understood and little studied. This is problematic, as phylogenies are crucial when evaluating evolutionary changes throughout time ( Purvis, Gittleman & Brooks, 2005 ; Mishra & Thines, 2014 ).…”

Section: Introductionmentioning

confidence: 99%

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The phylogenetics of Teleosauroidea (Crocodylomorpha, Thalattosuchia) and implications for their ecology and evolution

Johnson

Young

Brusatte

2020

PeerJ

107

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Teleosauroidea was a clade of ancient crocodylomorphs that were a key element of coastal marine environments during the Jurassic. Despite a 300-year research history and a recent renaissance in the study of their morphology and taxonomy, macroevolutionary studies of teleosauroids are currently limited by our poor understanding of their phylogenetic interrelationships. One major problem is the genus Steneosaurus, a wastebasket taxon recovered as paraphyletic or polyphyletic in phylogenetic analyses. We constructed a newly updated phylogenetic data matrix containing 153 taxa (27 teleosauroids, eight of which were newly added) and 502 characters, which we analysed under maximum parsimony using TNT 1.5 (weighted and unweighted analyses) and Bayesian inference using MrBayes v3.2.6 (standard, gamma and variation). The resulting topologies were then analysed to generate comprehensive higher-level phylogenetic hypotheses of teleosauroids and shed light on species-level interrelationships within the clade. The results from our parsimony and Bayesian analyses are largely consistent. Two large subclades within Teleosauroidea are recovered, and they are morphologically, ecologically and biogeographically distinct from one another. Based on comparative anatomical and phylogenetic results, we propose the following major taxonomic revisions to Teleosauroidea: (1) redefining Teleosauridae; (2) introducing one new family and three new subfamilies; (3) the resurrection of three historical genera; and (4) erecting seven new generic names and one new species name. The phylogeny infers that the Laurasian subclade was more phenotypically plastic overall than the Sub-Boreal-Gondwanan subclade. The proposed phylogeny shows that teleosauroids were more diverse than previously thought, in terms of morphology, ecology, dispersal and abundance, and that they represented some of the most successful crocodylomorphs during the Jurassic.

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“…The above analyses, similar to recent studies (Ősi et al, 2018;Foffa et al, 2019;Sachs et al, 2019a), find many aspects of the phylogeny to be consistent, including:…”

Section: Areas Of Uncertaintysupporting

confidence: 84%

Section: Introductioncontrasting

confidence: 63%

Section: Palaeoenvironment and The Importance Of Freshwater Teleosaurmentioning

confidence: 99%

Section: Character Sampling and Scoringmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The phylogenetics of Teleosauroidea (Crocodylomorpha, Thalattosuchia) and implications for their ecology and evolution

Johnson

Young

Brusatte

2020

PeerJ

107

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Cranial and endocranial anatomy of a three‐dimensionally preserved teleosauroid thalattosuchian skull

Wilberg

Beyl

Pierce

et al. 2021

The Anatomical Record

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Thalattosuchians represent one of the several independent transitions into the marine realm among crocodylomorphs. The extent of their aquatic adaptations ranges from the semiaquatic teleosauroids, superficially resembling extant gharials, to the almost cetacean‐like pelagic metriorhynchids. Understanding the suite of osteological, physiological, and sensory changes that accompanied this major transition has received increased attention, but is somewhat hindered by a dearth of complete three‐dimensionally preserved crania. Here, we describe the cranial and endocranial anatomy of a well‐preserved three‐dimensional specimen of Macrospondylus bollensis from the Toarcian of Yorkshire, UK. The trigeminal fossa contains two similar‐sized openings separated by a thin lamina of prootic, a configuration that appears unique to a subset of teleosauroids. Macrospondylus bollensis resembles other thalattosuchians in having pyramidal semicircular canals with elongate cochlear ducts, enlarged carotid canals leading to an enlarged pituitary fossa, enlarged orbital arteries, enlarged endocranial venous sinuses, reduced pharyngotympanic sinuses, and a relatively straight brain with a hemispherical cerebral expansion. We describe for the first time the olfactory region and paranasal sinuses of a teleosauroid. A relatively large olfactory region suggests greater capacity for airborne olfaction in teleosauroids than in the more aquatically adapted metriorhynchoids. Additionally, slight swellings in the olfactory region suggest the presence of small salt glands of lower secretory capacity than those of metriorhynchoids. The presence of osteological correlates for salt glands in a teleosauroid corroborates previous hypotheses that these glands originated in the common ancestor of Thalattosuchia, facilitating their rapid radiation into the marine realm.

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Reevaluation of the cranial osteology and phylogenetic position of the early crocodyliform Eopneumatosuchus colberti, with an emphasis on its endocranial anatomy

Melstrom

Turner

Irmis

2021

The Anatomical Record

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Eopneumatosuchus colberti Crompton and Smith, 1980, known from a single partial skull, is an enigmatic crocodylomorph from the Lower Jurassic Kayenta Formation. In spite of its unique morphology, an exceptionally pneumatic braincase, and presence during a critical time period of crocodylomorph evolution, relatively little is known about this taxon. Here, we redescribe the external cranial morphology of E. colberti, present novel information on its endocranial anatomy, evaluate its phylogenetic position among early crocodylomorphs, and seek to better characterize its ecology. Our examination clarifies key aspects of cranial suture paths and braincase anatomy. Comparisons with related taxa (e.g., Protosuchus haughtoni) demonstrate that extreme pneumaticity of the braincase may be more widespread in protosuchids than previously appreciated. Computed tomography scans reveal an endocranial morphology that resembles that of other early crocodylomorphs, in particular the noncrocodyliform crocodylomorph Almadasuchus figarii. There are, however, key differences in olfactory bulb and cerebral hemisphere morphology, which demonstrate the endocranium of crocodylomorphs is not as conserved as previously hypothesized. Our phylogenetic analysis recovers E. colberti as a close relative of Protosuchus richardsoni and Edentosuchus tienshanensis, contrasting with previous hypotheses of a sister group relationship with Thalattosuchia. Previous work suggested the inner ear has some similarities to semi-aquatic crocodyliforms, but the phylogenetic placement of E. colberti among protosuchids with a terrestrial postcranial skeletal morphology complicates paleoecological interpretation.

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The mystery of Mystriosaurus: redescribing the poorly known Early Jurassic teleosauroid thalattosuchians Mystriosaurus laurillardi and Steneosaurus brevior

Cited by 16 publications

References 0 publications

The phylogenetics of Teleosauroidea (Crocodylomorpha, Thalattosuchia) and implications for their ecology and evolution

The phylogenetics of Teleosauroidea (Crocodylomorpha, Thalattosuchia) and implications for their ecology and evolution

Cranial and endocranial anatomy of a three‐dimensionally preserved teleosauroid thalattosuchian skull

Reevaluation of the cranial osteology and phylogenetic position of the early crocodyliform Eopneumatosuchus colberti, with an emphasis on its endocranial anatomy

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