Geosaurinae Bonaparte, 1845

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 : 606

Geosaurinae Bonaparte, 1845 (Zoological Code)

Geosaurinae Bonaparte 1845: 4 , (as Geosaurina ), converted clade name (PhyloCode)

RegNum registration number 1020.

Type genus: Geosaurus Cuvier, 1824 .

Etymology

‘Pertaining to Geosaurus ’. The stem Geosaur - is based on the genus Geosaurus . - inae, is a Latin feminine plural suffix for ‘pertaining to’. Under Article 29.2 of the Zoological Code, the suffix - inae denotes a subfamily rank within the family-group.

Geological range

Middle Jurassic (early Bathonian) to Early Cretaceous (earliest Aptian) ( Cau and Fanti 2011, Chiarenza et al. 2015, Sachs et al. 2020).

PhyloCode phylogenetic definition

The largest clade within Metriorhynchidae containing Geosaurus giganteus ( von Sömmerring 1816) but not Rhacheosaurus gracilis von Meyer, 1831 , 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 (6): cranial rostrum with a mesorostrine condition created by elongation of the maxilla (shared with ‘ Cricosaurus ’ saltillensis ) (7.1); cranial rostrum wider than high (8.0); anterior margin of the choana is ‘M’-shaped (shared with Maledictosuchus ) (379.2); paroccipital process largely horizontal, with the lateral ends sharply inclined (415.2); surangular along the dorsal margin of the mandible does not extend anteriorly beyond the orbits (545.0); 20 or fewer maxillary alveoli (within Metriorhynchidae , shared with the Cretaceous rhacheosaurin) (594.1–3).

Potentially diagnostic characters

Depending on the phylogenetic position of the South American ‘ Metriorhynchus ’ species, the dentition having true denticles (653.1–2) could be diagnostic for Geosaurinae or a more inclusive subclade. The posterior cervical vertebral centra being subequal in length and width (699.1) may be diagnostic to Geosaurinae , within Metriorhynchidae this character is only known amongst geosaurines.

Composition

Neptunidraco , the subclade Geosaurini , and multiple taxa that do not have a valid generic assignment (e.g. ‘ Metriorhynchus ’ brachyrhynchus, the ‘E’-clade, and the indeterminate specimens in Plesiosuchina and Dakosaurina ).

Comments

Authorship: The nomen Geosaurinae was first used by Bonaparte (1845: 4), as Geosaurina , not Lydekker (1888a) as reported by Young and Andrade (2009).

Prior phylogenetic definition: Young and Andrade (2009) defined Geosaurinae as the most inclusive clade, including Geosaurus giganteus ( von Sömmerring 1816) , but not Metriorhynchus geoffroyii von Meyer, 1832 . Here we have added Rhacheosaurus gracilis and Gracilineustes leedsi as external specifiers, as they are now internal specifiers for Metriorhynchinae .

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/.