Charitomenosuchus

Charitomenosuchus Temporal range: Middle Jurassic, middle Callovian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Holotype skull and vertebra
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauria
Clade:	Pseudosuchia
Clade:	Crocodylomorpha
Suborder:	† Thalattosuchia
Family:	† Machimosauridae
Genus:	† Charitomenosuchus Johnson et al., 2020
Species:	†C. leedsi
Binomial name
†Charitomenosuchus leedsi (Andrews, 1909)
Synonyms
Steneosaurus leedsiAndrews, 1909 Steneosaurus teleosauroidesAuer, 1909 Steneosaurus pictaviensisVignaud, 1998

Charitomenosuchus (meaning "graceful crocodile") is an extinct genus of machimosaurid teleosauroid from the Callovian Oxford Clay Formation of England. ^[1]

Illustration of the holotype

History

The type species was originally named "Steneosaurus" leedsi by Andrews in 1909 on the basis of three specimens. ^[2] The genus Steneosaurus was used as a longtime wastebasket taxon for various teleosauroid specimens and had more than a dozen species. The type species, Steneosaurus rostromajor is undiagnostic, making the genus and species dubious and invalid. Additionally, many species of so called "Steneosaurus" were found to be quite different and unrelated to one another, thus needing new generic names. ^[1] .

In her unpublished 2019 thesis, Michela Johnson coined the nomen ex dissertationae Charitomenosuchus for S. leedsi. ^[3] The new genus and combination, Charitomenosuchus leedsi was formally published by Johnson and colleagues in 2020. ^[1]

Classification

Charitomenosuchus is classified as one of the most basal machimosaurids, being outside the subfamily Machimosaurinae. It's more gracile and lightly-built morphology is typical of basal machimosaurids while more derived members were large and much more robust.

The cladogram below is from an analysis by Johnson and colleagues in 2020. ^[1]

Machimosauridae	Macrospondylus bollensis Clovesuurdameredeor stephani Charitomenosuchus leedsi Seldsienean megistorhynchus Deslongchampsina larteti Machimosaurinae Proexochokefalos hebertii cf. Proexochokefalos bouchardi Neosteneosaurus edwardsi Andrianavoay baroni Machimosaurini Lemmysuchus obtusidens Yvridiosuchus boutilieri Machimosaurus buffetauti Machimosaurus mosae Machimosaurus rex Machimosaurus hugii

Ecology

In life, Charitomenosuchus was a marine hunter of small prey. It had proportionally one of the most gracile jaws of all machimosaurids, with a quick bite but relatively weak bite force. Additionally, it had a relatively weak front bite, meaning it could grab prey quickly but likely took longer to overpower and process. This suggests that Charitomenosuchus was adapted for catching quick prey such as small fish and cephalopods that it coexisted with. ^[4]

References

1. Johnson, Michela M.; Young, Mark T.; Brusatte, Stephen L. (2020). "The phylogenetics of Teleosauroidea (Crocodylomorpha, Thalattosuchia) and implications for their ecology and evolution". PeerJ. 8: e9808. doi: 10.7717/peerj.9808 . PMC   7548081 . PMID   33083104.
2. C. W. Andrews. 1909. On some new steneosaurs from the Oxford Clay of Peterborough. Annals and Magazine of Natural History 3:299-308
3. Johnson, Michela Maria Angeline (2019). "The taxonomy, systematics and ecomorphological diversity of Teleosauroidea (Crocodylomorpha, Thalattosuchia), and the evaluation of the genus 'Steneosaurus'". Archives of the University of Edinburgh .
4. Johnson, M. M.; Foffa, D.; Young, M. T.; Brusatte, S. L. (2022). "The ecological diversification and evolution of Teleosauroidea (Crocodylomorpha, Thalattosuchia), with insights into their mandibular biomechanics". Ecology and Evolution. 12 (11): e9484. Bibcode:2022EcoEv..12E9484J. doi: 10.1002/ece3.9484 . hdl: 20.500.11820/07ef2706-2019-40ec-add6-6eb522f6f193 . PMC   9674474 . PMID   36415878.