Rhacheosaurini Young et al. 2011a

Young, Mark T., Wilberg, Eric W., Johnson, Michela M., Herrera, Yanina, Brandalise, Marco de Andrade, Brignon, Arnaud, Sachs, Sven, Abel, Pascal, Foffa, Davide, Fernández, Marta S., Vignaud, Patrick, Cowgill, Thomas & Brusatte, Stephen L., 2024, The history, systematics, and nomenclature of Thalattosuchia (Archosauria: Crocodylomorpha), Zoological Journal of the Linnean Society 200 (2), pp. 547-617 : 603-606

Rhacheosaurini Young et al. 2011a (Zoological Code)

Rhacheosaurini Young et al. 2011a: 914 , converted clade name (PhyloCode)

RegNum registration number 1019.

Type genus: Rhacheosaurus von Meyer, 1831 .

Etymology

‘Pertaining to Rhacheosaurus ’. The stem Rhacheosaur - is based on the genus Rhacheosaurus . - ini is a Latin masculine plural suffix for ‘pertaining to’. Under Article 29.2 of the Zoological Code, the suffix - ini denotes a tribe rank within the family-group.

Geological range

Late Jurassic (late Kimmeridgian) to Early Cretaceous (early Valanginian) ( Young et al. 2010, Sachs et al. 2020).

PhyloCode phylogenetic definition

The largest clade within Metriorhynchidae containing Rhacheosaurus gracilis von Meyer, 1831 , but not Metriorhynchus brevirostris ( Holl 1829) , and Gracilineustes leedsi ( Andrews 1913) .

Reference phylogeny

Fig. 3 .

Zoological Code diagnosis and PhyloCode diagnostic apomorphies

Metriorhynchid crocodylomorphs with the following unique combination of characters (5): external nares oriented dorsally (shared with derived members of the ‘E’-clade) (95. 2); posterodorsal retraction of the posterior margin of the narial fossa (shared with the ‘E’-clade) (104.3–6); external nares have a fully ossified internarial premaxillary bar (105.2); absence of a constriction at the premaxilla–maxilla suture (shared with the ‘E’-clade, Plesiosuchus and Dakosaurus ) (114.0); one-third or less of total premaxilla length is posterior to the external nares (127.3).

Potentially diagnostic characters

The following four characters may be diagnostic for Rhacheosaurini , however, at present we do not know if they could be more widely distributed within Metriorhynchinae or more restricted to the Rhacheosaurus + Cricosaurus subclade. Only the discovery of more complete specimens within Rhacheosaurini , and non-rhacheosaurin metriorhynchines will answer this: 25 presacral vertebrae (686.1); increase in the number of caudal vertebrae, such that there are 50 or more (713.1); humerus proximal region confined to the proximal surface (753.0); humerus diaphysis contributes less than 25% of total humerus length (758.2). The character: anterior margin of the frontoparietal fossae (in dorsal view) terminates level to the postorbital anterior margin, or anterior to it (192.2), is equivocal due to the instability within Metriorhynchinae , and which taxa fall within Rhacheosaurini .

Composition

Rhacheosaurus , Cricosaurus , and multiple taxa that do not have a valid generic assignment (e.g. ‘ Metriorhynchus ’ palpebrosus , ‘ Cricosaurus ’ saltillensis , and the Cretaceous rhacheosaurin).

Comments

Authorship: The nomen Rhacheosaurini was first used by Young et al. (2011).

Prior phylogenetic definition: Young et al. (2011a) defined Rhacheosaurini as the most inclusive clade, including Rhacheosaurus gracilis von Meyer, 1831 but not Metriorhynchus geoffroyii von Meyer, 1832 , and Gracilineustes leedsi ( Andrews 1913) .

Figures

Figure 3. The equal weights, no constraints strict consensus topology (C0). Length = 4164, CI = 0.303, RI = 0.831, RC = 0.251, HI = 0.697, number of most parsimonious cladograms hit the hold limit.Phylogeny pruned to highlight Thalattosuchia (see Supporting Information, Appendix S2, Fig. S1 for the entire topology). A, Crocodylomorpha; B, Crocodyliformes; C, Thalattosuchia; D, Neothalattosuchia; E, Teleosauridae; F, Teleosaurinae; G, Aeolodontini; H, Machimosauridae; I, Machimosaurinae; J, Machimosaurini; K, Euthalattosuchia; L, Metriorhynchidae; M, Metriorhynchinae; N, Rhacheosaurini; O, Geosaurinae; P, Geosaurini. Green lines highlight non-neothalattosuchian thalattosuchians, orange lines highlight teleosauroid thalattosuchians, and blue lines highlight metriorhynchoid thalattosuchians.Images from PhyloPics.org, with the teleosauroid by Scott Hartman, and the metriorhynchid by Dmitry Bogdanov (vectorized by T. Michael Keesey), the only change made was to their colouration, and their license is: https://creativecommons.org/licenses/by/3.0/.