Systematics and Taxonomy of Eocene Tomistomine Crocodylians From Britain and Northern Europe

Brochu, Christopher A.

doi:10.1111/j.1475-4983.2007.00679.x

Cited by 35 publications

(37 citation statements)

References 22 publications

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“…2B,C). The dorsoventral expansion of the sulcus is variable among species, tending to be wider in larger specimens of horned crocodylids, such as Crocodylus rhombifer (Cuvier, 1807) and Crocodylus siamensis (Schneider, 1801), and it flares anteriorly in Tomistoma schlegelii (M€ uller, 1838;Brochu, 2006Brochu, , 2007Brochu et al 2010).…”

Section: Osteologymentioning

confidence: 99%

The evolution of the meatal chamber in crocodyliforms

2016

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The unique outer ear of crocodylians consists of a large meatal chamber (MC) concealed by a pair of muscular earlids that shape a large part of the animal's head. This chamber is limited medially by the enlarged tympanic membrane. Yet, the anatomy of this distinctive and complex region is underexplored and its evolutionary history untraced. The osteology and soft tissues of the MC in extant crocodylians was analysed to describe it and establish osteological correlates within this region. A broad survey of the osteological correlates was conducted in major clades of fossil crocodyliforms to estimate evolutionary trends of the MC. The reorganization of the MC at the origin of crocodyliforms includes characters also present in more basal taxa such as 'sphenosuchians' as well as unique traits of crocodyliforms. Three major patterns are recognized in the MC of basal mesoeucrocodylians. The distinct 'thalattosuchian pattern' indicates that extensive modifications occurred in this clade of aquatic fossil crocodyliforms, even when multiple alternative phylogenetic positions are taken into account. Some traits already established in putative closely related clades are absent or modified in this group. The 'basal notosuchian/sebecian pattern' is widespread among basal metasuchians, and establishes for the first time characters maintained later in neosuchians and extant forms. The 'advanced notosuchian pattern' includes modifications of the MC possibly related to a terrestrial lifestyle and potentially a structure analogous to the mammalian pinna. The main variation in the MC of neosuchians is associated with the homoplastic secondary opening of the cranioquadrate passage. The inferred phylogenetic trends in the crocodyliform MC suggest the great anatomical disparity in this region followed a complex evolutionary pattern, and tympanic hearing played an important role in the origin and diversification of Crocodyliformes.

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Section: Osteologymentioning

confidence: 99%

The evolution of the meatal chamber in crocodyliforms

2016

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“…Its lacrimal is three times wider than long (four in M. zennaroi ), and slightly wider than the prefrontal at the level of the anterior margin of the orbits (more than twice the width in M. zennaroi ). The snout is more robust in the Issel skull, and the constriction at the level of the seventh–eighth maxillary teeth is stronger than in Dollosuchoides densmorei Brochu, , and all more derived tomistomines. The frontal does not reach the anterior level of the prefrontal, whereas it exceeds it strongly in Megadontosuchus arduini (de Zigno, ).…”

Section: Comparison and Taxonomic Considerationsmentioning

confidence: 90%

“…In the most primitive tomistomine Maroccosuchus zennaroi Jonet & Wouters, , the symphysis reaches the level of the ninth tooth and the splenial reaches the level of the seventh tooth. The symphysis in ‘ Atacisaurus glareae ’ is nearly as long as in Dollosuchoides densmorei Brochu, (reaches the level of the ninth or tenth tooth), in which the splenial stops at the level of the eighth tooth. In a specimen from the Ypresian of La Borie (Southern France), and referred to K. spenceri (Laurent et al ., ), the symphysis and the splenial lengths are the same as in ‘ A. glareae ’, reaching, respectively, the tenth and the seventh teeth (S. Jouve, pers.…”

Section: Comparison and Taxonomic Considerationsmentioning

confidence: 99%

“…It also bears several common characters with this species. The maxillary process in the lacrimal is located at the anteriormost extent of the lacrimal, and the prefrontal is nearly as long as the lacrimal, two diagnostic characters of the until now monospecific genus Kentisuchus (Brochu, ). Unfortunately, the other K. spenceri character, the M‐shape of the skull table in occipital view, cannot be observed in MHNT.PAL.2010.0.49 because of the poor preservation of the occipital portion, and, in particular, the poor preservation of the squamosals.…”

Section: Comparison and Taxonomic Considerationsmentioning

confidence: 99%

“…The most primitive tomistomines, Maroccosuchus zennaroi Jonet and Wouters, and Kentisuchus spenceri (Buckland, ), are known from the lower Eocene of the west Tethys/north‐East Atlantic area (Europe and North Africa), suggesting a west Peri‐Tethyan origin for the tomistomines (Jouve et al ., ). The genus Kentisuchus is known in the Ypresian from the Isle of Sheppey (England) (see Brochu, ), and some remains have been described from Southern France (Laurent et al ., ), and perhaps also from Northern Spain (Costa et al ., ; see Jouve et al ., ). A skull from the late Lutetian of Issel (south of France), first described as ‘ Atacisaurus glareae ’ (Astre, ), has been cited as a possible Kentisuchus (Jouve, ).…”

Section: Introductionmentioning

confidence: 99%

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A new basal tomistomine (Crocodylia, Crocodyloidea) from Issel (Middle Eocene; France): palaeobiogeography of basal tomistomines and palaeogeographic consequences

Jouve

2016

Zool J Linn Soc

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A skull and mandible of a crocodylian from the late Lutetian of Issel, previously described as 'Atacisaurus glareae' is reconsidered. The holotype of 'A. glareae', a partial mandible, is lost, and the skull cannot be designated as a lectotype for the species. 'Atacisaurus glareae' is thus a nomen dubium. The skull bears a combination of characters, allowing us to assign it to the genus Kentisuchus. It differs from the, until now, only known species Kentisuchus spenceri from the Ypresian of England, in having a more robust snout, with the constriction of the snout at the level of the seventh-eighth teeth being 80% of the largest maxillary width, and not bearing anteroposterior shallow fossae along the lacrimomaxillary sutures. A new species is thus erected, Kentisuchus astrei sp. nov. Phylogenetic analysis confirms that the genus Kentisuchus is one of the most primitive tomistomine. The phylogenetic and palaeogeographic distribution suggests that Kentisuchus was isolated in the Atlantic Ocean, and Ebro (Spain) and Aquitaine (France) basins, during the Ypresian, and that the south Pyrenean marine corridor between the Atlantic Ocean and the Tethys could have closed during the early Ypresian, earlier than previously supposed. This could be correlated with the first mammal migrations from the Iberian Peninsula to Southern France. The palaeogeographic distribution of early and middle Eocene tomistomines also suggests the possible presence of a marine corridor between the North Sea and the Central Tethys through the Polish Lowlands Basin during the early Lutetian. This marine corridor could be informative for studies on mammal migration, as the presence of a north-south marine corridor necessarily means there is an absence or less efficient east-west terrestrial passage. This could have consequences on the history of Asian-European mammal migrations.

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Cranial anatomy of the mekosuchine crocodylianTrilophosuchus rackhamiWillis, 1993

Ristevski

Weisbecker

Scanlon³

et al. 2022

The Anatomical Record

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One of the best-preserved crocodylian fossil specimens from the Cenozoic of Australia is the holotype of the mekosuchine Trilophosuchus rackhami, from the middle Miocene (13.56 ± 0.67 Ma) Ringtail Site at Riversleigh, northwestern Queensland. Although lacking most of the snout, the holotype skull of T. rackhami (QMF16856) has an exceptionally well-preserved cranium. Micro-CT scanning of the holotype has allowed for all the preserved cranial bones to be digitally disarticulated, facilitating an unprecedented insight into the cranial anatomy of not just T. rackhami, but any mekosuchine. Trilophosuchus rackhami was a small-bodied crocodylian and one of the most morphologically distinct mekosuchines, characterized by a unique combination of cranial characteristics several of which are exclusive to the species. Fossil material that is definitively referrable to the species T. rackhami is currently known solely from the middle Miocene Ringtail Site. However, an isolated parietal from Hiatus Site at Riversleigh demonstrates that Trilophosuchus also occurred during the late Oligocene ($25 Ma), extending the range of the genus by more than 10 million years. The new description of T. rackhami also allowed for a reevaluation of its phylogenetic relationships. Our results reaffirm the placement of T. rackhami as a member of Mekosuchinae within the subclade Mekosuchini. In all analyses, Mekosuchinae was consistently found to be monophyletic and part of the larger crocodylian clade Longirostres. However, the assignment of Mekosuchinae as a subset of Crocodylidae is brought into question, suggesting that the status of Mekosuchinae as a subfamily should be reconsidered.

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Systematics and Taxonomy of Eocene Tomistomine Crocodylians From Britain and Northern Europe

Cited by 35 publications

References 22 publications

The evolution of the meatal chamber in crocodyliforms

The evolution of the meatal chamber in crocodyliforms

A new basal tomistomine (Crocodylia, Crocodyloidea) from Issel (Middle Eocene; France): palaeobiogeography of basal tomistomines and palaeogeographic consequences

Cranial anatomy of the mekosuchine crocodylianTrilophosuchus rackhamiWillis, 1993

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