Gracilineustes

Gracilineustes is an extinct genus of marine crocodyliform that lived in the oceans during the Middle to Late Jurassic. Gracilineustes was a carnivore that spent much, if not all, its life out at sea. It was a small reptile, with G. leedsi measuring 2.25–3.11 m (7.4–10.2 ft) long and G. acutus measuring 3.77 m (12.4 ft) long.^[3]

Skull and limb of G. leedsi

Gracilineustes Temporal range: Callovian - Kimmeridgian, 167–155 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Fossil skull of G. leedsi, NHMUK PV R5793, at the Field Museum of Natural History
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauria
Clade:	Pseudosuchia
Clade:	Crocodylomorpha
Suborder:	†Thalattosuchia
Family:	†Metriorhynchidae
Subfamily:	†Metriorhynchinae
Genus:	†Gracilineustes Young et al., 2010
Type species
†Gracilineustes leedsi (Andrews, 1913)[1]
Other species
†G. acutus Lennier, 1887 [2]
Synonyms
Metriorhynchus laeve Andrews, 1913

Holotype of G. leedsi, NHMUK PV R3540

Discovery and species

Fossil specimens referrable to Gracilineustes are known from Middle-Late Jurassic deposits of England and France.^[4]

Valid species

• G. leedsi: Western Europe (England) of the Middle Jurassic (Callovian);^[1] Metriorhynchus laeve is a junior synonym.
• G. acutus: Western Europe (France) of the Late Jurassic (Kimmeridgian) ^[2]

Classification

Gracilineustes is an early member of the metriorhynchid subfamily Metriorhynchinae. The cladogram below is from an analysis by Mark Young and colleagues in 2020.^[5]

Metriorhynchinae

Thalattosuchus superciliosus Gracilineustes acutus Gracilineustes leedsi Maledictosuchus nuyivijanan Maledictosuchus riclaensis Metriorhynchus brevirostris Rhacheosaurini "Metriorhynchus" palpebrosus "Cricosaurus" saltillensis Swiss rhacheosaurin Cretaceous rhacheosaurin Metriorhynchinae indet. (Cuba) Rhacheosaurus gracilis cf. Cricosaurus Cricosaurus Cricosaurus bambergensis Solnhofen Cricosaurus Cricosaurus elegans Cricosaurus suevicus Cricosaurus lithographicus Cricosaurus araucanensis Cricosaurus vignaudi Cricosaurus schroederi