Metriorhynchidae

Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period (Bajocian to Valanginian stages, potentially as late as early Aptian[2]) of Europe, North America and South America. The name Metriorhynchidae was coined by the Austrian zoologist Leopold Fitzinger in 1843.[3] The group contains two subfamilies, the Metriorhynchinae and the Geosaurinae.[4][5]

Metriorhynchids Temporal range: Middle Jurassic-Early Cretaceous, 170–135 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Dakosaurus maximus skull, Staatliches Museum für Naturkunde Stuttgart
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Suborder:	†Thalattosuchia
Superfamily:	†Metriorhynchoidea
Family:	†Metriorhynchidae Fitzinger, 1843
Subfamilies
†Geosaurinae †Metriorhynchinae
Synonyms
Geosauridae Andrews, 1913[1]

Description

Metriorhynchids are fully aquatic crocodyliforms. Their forelimbs were small and paddle-like, and unlike living crocodilians, they lost their osteoderms ("armour scutes"). Their body shape maximised hydrodynamy (swimming efficiency), as they did have a shark-like tail fluke.[6]

Metriorhynchids were the only group of archosaurs to become fully adapted to the marine realm, becoming pelagic in lifestyle.[7] With tail flukes, reduced limb musculature, and long bones histologically comparable to other obligately aquatic animals, they were almost certainly incapable of terrestrial locomotion; combined with an unusually tall hip opening, as also seen in other obligately aquatic reptiles including the viviparous Keichousaurus, this has lent credence to the suggestion that metriorhynchids gave live birth.[8] Recent research posits that despite their successful adaptation to a pelagic lifestyle, basal metriorhynchids were uniquely disadvantaged among aquatic tetrapods in evolving into sustained swimmers due to little to no posterodorsal retraction of the external nares (unlike other reptilian groups such as mesosaurs, phytosaurs, thalattosaurians, saurosphargids, ichthyosauriforms, sauropterygians, pleurosaurids or mosasauroids, as well as mammalian cetaceans or sirenians).[9]

The family has a wide geographic distribution, with material found in Argentina, Chile, Cuba, England, France, Germany, Italy, Mexico, Poland, Russia and Switzerland.[7][5]

Classification

Phylogenetic analyses published during the 2000s cast doubt on the idea that many traditional metriorhynchid genera formed natural groups (i.e., include all descendants of a common ancestor). The traditional species of Geosaurus,[10][11][12] Dakosaurus[10] and Cricosaurus[10] were found to represent unnatural groups, and the species traditionally classified in these genera were reshuffled in a study published in November 2009 by Mark T. Young and Marco Brandalise de Andrade.[4] The monophyly of Metriorhynchus [10][11][13] and Teleidosaurus[10][12] is also unsupported, and the species of these genera are pending reclassification.[4]

The classification presented by Young and Andrade in 2009 was approved in later studies of the Metriorhynchidae.[5][14][15] Metriorhynchidae is a node-based taxon defined in 2009 as the least inclusive clade consisting of Metriorhynchus geoffroyii and Geosaurus giganteus.[4] The cladogram below follows the topology from a 2020 analysis by Young et al. and reduced to genera only.[9]

Metriorhynchidae	Metriorhynchinae    Metriorhynchus       Gracilineustes    Rhacheosaurini    Maledictosuchus       Cricosaurus     Rhacheosaurus            Geosaurinae    Neptunidraco      Geosaurini      Tyrannoneustes       Torvoneustes     'E-clade'     Purranisaurus             Ieldraan     Geosaurus         Dakosaurus       Plesiosuchus     Suchodus

List of genera

The type genus of the family Metriorhynchidae is Metriorhynchus from the Middle to Late Jurassic.[7] Other genera included within this family are Cricosaurus, Geosaurus, and Dakosaurus. Though once considered a metriorhynchid, Teleidosaurus has since been found to be slightly more distantly related to these animals within the superfamily Metriorhynchoidea.

Within this family, the genus Neustosaurus is considered nomen dubium ("doubtful name").[16]

The genus Capelliniosuchus was once thought to be a metriorhynchid similar to Dakosaurus.[17] However, Sirotti demonstrated that it is a junior synonym of Mosasaurus.[18]

Genus	Status	Author	Age	Location	Description	Synonyms	Images
Aggiosaurus		Ambayrac, 1913	late Oxfordian	France.	Sometimes considered to be a nomen dubium.		Cricosaurus suevicus Dakosaurus andiniensis Metriorhynchus superciliosus Neptunidraco ammoniticus Purranisaurus casamiquelai Suchodus durobrivensis
Cricosaurus	Valid	Wagner, 1858	middle Oxfordian to upper Valanginian	Argentina, Chile, Cuba, England, France, Germany, Mexico, Russia and Switzerland.
Dakosaurus[19]	Valid	von Quenstedt, 1856	lower Oxfordian to lower Berriasian	Argentina, England, France, Germany, Mexico, Poland, Switzerland and possibly Russia.		Dacosaurus (lapsus calami)
Enaliosuchus[20]	nomen dubium[21]	Koken, 1883	Valanginian	Germany.
Geosaurus[22]	Valid	Cuvier, 1824	upper Kimmeridgian to upper Valanginian	France, Germany, Italy and Switzerland.		Brachytaenius Halilimnosaurus
Gracilineustes[23]	Valid	Young et al., 2010	lower Kimmeridgian	England and France.
Maledictosuchus	Valid	Parrilla-Bel et al., 2013		Spain.
Metriorhynchus[24]	Valid	von Meyer, 1830	lower Callovian to upper Kimmeridgian.	England, France, Germany and Switzerland.		Metiorychus (lapsus calami)
Neptunidraco[14]	Valid	Cau & Fanti, 2011	late Bajocian to earliest Bathonian	Italy.
Neustosaurus	nomen dubium				— potential senior synonym of Cricosaurus
Plesiosuchus	Valid	Owen, 1884	late Kimmeridgian to early Tithonian	England and possibly Spain.
Purranisaurus	Valid	Rusconi, 1948	lower Callovian to lower Tithonian	Argentina and Chile.
Rhacheosaurus	Valid	von Meyer, 1831	lower Tithonian	Germany.
Suchodus	Valid	Lydekker, 1890	lower Callovian to lower Oxfordian	England and France.
Torvoneustes[25]	Valid	Andrade et al., 2010	upper Kimmeridgian	England.
Tyrannoneustes	Valid	Young et al., 2013	Callovian	England.

See also

• List of marine reptiles

References

1. Andrews CW. 1913. A descriptive catalogue of the marine reptiles of the Oxford Clay, Part Two. London: British Museum (Natural History), 206 pp.
2. Alfio A. Chiarenza, Davide Foffa, Mark T. Young, Gianni Insacco, Andrea Cau, Giorgio Carnevale, Rita Catanzariti (2015). "The youngest record of metriorhynchid crocodylomorphs, with implications for the extinction of Thalattosuchia". Cretaceous Research. 56: 608–616. doi:10.1016/j.cretres.2015.07.001.CS1 maint: uses authors parameter (link)
3. Fitzinger LJFJ. 1843. Systema Reptilium. Wien: Braumüller et Seidel, 106 pp.
4. Mark T. Young and Marco Brandalise de Andrade (2009). "What is Geosaurus? Redescription of Geosaurus giganteus (Thalattosuchia: Metriorhynchidae) from the Upper Jurassic of Bayern, Germany". Zoological Journal of the Linnean Society. 157 (3): 551–585. doi:10.1111/j.1096-3642.2009.00536.x.CS1 maint: uses authors parameter (link)
5. Mark T. Young, Stephen L. Brusatte, Marcello Ruta and Marco Brandalise de Andrade (2010). "The evolution of Metriorhynchoidea (Mesoeucrocodylia, Thalattosuchia): an integrated approach using geometrics morphometrics, analysis of disparity and biomechanics". Zoological Journal of the Linnean Society. 158 (4): 801–859. doi:10.1111/j.1096-3642.2009.00571.x.CS1 maint: uses authors parameter (link)
6. Fraas E (1902). "Die Meer-Krocodilier (Thalattosuchia) des oberen Jura unter specieller Berücksichtigung von Dacosaurus und Geosaurus". Palaeontographica. 49: 1–72.
7. Steel R. 1973. Crocodylia. Handbuch der Paläoherpetologie, Teil 16. Stuttgart: Gustav Fischer Verlag,116 pp.
8. Herrera, Y.; Fernandez, M.S.; Lamas, S.G.; Campos, L.; Talevi, M.; Gasparini, Z. (2017). "Morphology of the sacral region and reproductive strategies of Metriorhynchidae: a counter-inductive approach". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 106 (4): 247–255. doi:10.1017/S1755691016000165.
9. Young, M.T.; Sachs, S.; Abel, P.; Foffa, D.; Herrera, Y.; Kitson, J.J.N. (2020). "Convergent evolution and possible constraint in the posterodorsal retraction of the external nares in pelagic crocodylomorphs". Zoological Journal of the Linnean Society. 189 (2): 494–520. doi:10.1093/zoolinnean/zlaa021.
10. Young MT (2007). "The evolution and interrelationships of Metriorhynchidae (Crocodyliformes, Thalattosuchia)". Journal of Vertebrate Paleontology. 27 (3): 170A. doi:10.1080/02724634.2007.10010458.
11. Wilkinson LE, Young MT, Benton MJ (2008). "A new metriorhynchid crocodilian (Mesoeucrocodylia: Thalattosuchia) from the Kimmeridgian (Upper Jurassic) of Wiltshire, UK". Palaeontology. 51 (6): 1307–1333. doi:10.1111/j.1475-4983.2008.00818.x.
12. Mueller-Töwe IJ (2005). "Phylogenetic relationships of the Thalattosuchia". Zitteliana. A45: 211–213.
13. Gasparini Z, Pol D, Spalletti LA (2006). "An unusual marine crocodyliform from the Jurassic-Cretaceous boundary of Patagonia". Science. 311 (5757): 70–73. doi:10.1126/science.1120803. PMID 16282526.
14. Andrea Cau; Federico Fanti (2011). "The oldest known metriorhynchid crocodylian from the Middle Jurassic of North-eastern Italy: Neptunidraco ammoniticus gen. et sp. nov". Gondwana Research. 19 (2): 550–565. doi:10.1016/j.gr.2010.07.007.
15. Mark T. Young, Mark A. Bell and Stephen L. Brusatte (2011). "Craniofacial form and function in Metriorhynchidae (Crocodylomorpha: Thalattosuchia): modelling phenotypic evolution with maximum-likelihood methods". Biology Letters. 7 (6): 913–916. doi:10.1098/rsbl.2011.0357. PMC 3210659. PMID 21543396.CS1 maint: uses authors parameter (link)
16. Buffetaut E (1982). "Radiation évolutive, paléoécologie et biogéographie des Crocodiliens mésosuchienes". Mémoires Societé Geologique de France. 142: 1–88.
17. Simonelli V (1896). "Intoro agli avanzi di coccodrilliano scoperti a San Valentino (provincial di Reggio Emilia) nel 1886". Atli della Reale Accademia dei Lincei, Series Qunita Rendiconti. 5 (2): 11–18.
18. Sirotti A. 1989. Mosasaurus hoffmanni Mantell, 1828 (Reptilia) nelle <<argille scagliose>> di S. Valentino (Reggio E.). Atti della società dei naturalisti e matematici di Modena 120: 135-146.
19. Quenstedt FA. 1856. Sonst und Jetzt: Populäre Vortäge über Geologie. Tübingen: Laupp, 131.
20. Koken E (1883). "Die reptilian der norddeutschen unteren Kreide". Zeitschrift Deutschen Geologischen Gesellschaft. 35: 735–827.
21. Sachs S, Young MT, Hornung JJ (2020). "The enigma of Enaliosuchus, and a reassessment of the Lower Cretaceous fossil record of Metriorhynchidae". Cretaceous Research. 114: 104479.CS1 maint: multiple names: authors list (link)
22. Cuvier G. 1824. Sur les ossements fossiles de crocodiles, 5. In: Dufour & D'Occagne, eds. Recherches sur les ossements fossiles, 2nd édition. Paris: 143-160
23. Young Mark T., Brusatte Stephen L., Ruta M., Andrade Marco B. (2009). "The evolution of Metriorhynchoidea (Mesoeucrocodylia, Thalattosuchia): an integrated approach using geometrics morphometrics, analysis of disparity and biomechanics". Zoological Journal of the Linnean Society. 158 (4): 801–859. doi:10.1111/j.1096-3642.2009.00571.x.CS1 maint: multiple names: authors list (link)
24. Von Meyer H (1830). "Achte Versammlung der Naturforscher und Aerzte zu Heidelberg im September 1829". Isis von Oken. 1830: 517–519.
25. Andrade, M.B.D.; Young, M.T.; Desojo, J.B.; Brusatte, S.L. (2010). "The evolution of extreme hypercarnivory in Metriorhynchidae (Mesoeucrocodylia: Thalattosuchia) based on evidence from microscopic denticle morphology". Journal of Vertebrate Paleontology. 30 (5): 1451–1465. doi:10.1080/02724634.2010.501442.