''Cricosaurus'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of marine crocodyliforms of the

Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...

. belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Metriorhynchidae Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period ( Bajocian to early Aptian) of Europe, North America and South America. The name Metriorhynchid ...

. The genus was established by

Johann Andreas Wagner Johann Andreas Wagner (21 March 1797 – 17 December 1861) was a German palaeontologist, zoologist and archaeologist who wrote several important works on palaeontology. He was also a pioneer of biogeographical theory. Career Wagner was born ...

in 1858 for three skulls from the

Tithonian In the geological timescale, the Tithonian is the latest age (geology), age of the Late Jurassic Epoch and the uppermost stage (stratigraphy), stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 annum, Ma and 143.1 ±0.6 (mi ...

(

) of

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. The name ''Cricosaurus'' means "Ring lizard", and is derived from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

'- ("ring") and -' ("lizard"). It was a relatively small reptile, with ''C. suevicus'' and ''C. araucanensis'' measuring and in total body length, respectively.

Discovery

''Cricosaurus'' was first named by Wagner in 1858,Wagner A. 1858. Zur Kenntniss der Saurier aus den lithographischen Schiefern. ''Abhandlungen der Mathemat.-Physikalischen Classe der Königlich Bayerischen Akademie der Wissenschaften'' 8: 415-528. as a reclassification of a specimen he had previously described in 1852 ("Stenosaurus" ''elegans'', "Stenosaurus" being a misspelling of ''

Steneosaurus ''Steneosaurus'' (from , 'narrow' and , 'lizard') is a dubious genus of teleosaurid crocodyliform from the Middle or Late Jurassic (Callovian or early Oxfordian) of France. The genus has been used as a wastebasket taxon for thalattosuchian ...

'').Wagner A. 1852. Neu-aufgefundene Saurier-Überreste aus dem lithographischen Schiefern und dem oberen Jurakalk. ''Abhandlungen der Mathemat.-Physikalischen Classe der Königlich Bayerischen Akademie der Wissenschaften'' 6: 661-710. Several other species have since been named, including ''C. suevicus'' by Fraas in 1901 (originally as a species of ''Geosaurus'').Fraas E. 1901. Die Meerkrokodile (Thalattosuchia n. g.) eine neue Sauriergruppe der Juraformation. ''Jahreshefte des Vereins für vaterländische Naturkunde, Württemberg'' 57: 409-418. One former species, ''C. medius'' (named by Wagner in 1858) has since been reclassified as a junior synonym of '' Rhacheosaurus gracilis''. Fossil specimens referrable to ''Cricosaurus'' are known from Late Jurassic deposits in

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

(

Vaca Muerta The Vaca Muerta Formation, commonly known as Vaca Muerta ( Spanish for ''dead cow''), is a geologic formation of Late Jurassic to Early Cretaceous age, located in the Neuquén Basin in northern Patagonia, Argentina. It is well known as the host ...

),Gasparini ZB, Dellapé D. 1976. Un nuevo cocodrilo marino (Thalattosuchia, Metriorhynchidae) de la Formación Vaca Muerta (Jurasico, Tithoniano) de la Provincia de Neuquén (República Argentina). ''Congreso Geológico Chileno'' 1: c1-c21.

Cuba Cuba, officially the Republic of Cuba, is an island country, comprising the island of Cuba (largest island), Isla de la Juventud, and List of islands of Cuba, 4,195 islands, islets and cays surrounding the main island. It is located where the ...

(

Jagua Formation The Jagua Formation is a Late Jurassic (middle to late Oxfordian (stage), Oxfordian) geologic Formation (geology), formation in the Sierra de los Órganos and Sierra del Rosario mountain ranges in Pinar del Río Province, western Cuba. Plesiosaur ...

), and

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

( La CajaBuchy, M. C., Vignaud, P., Frey, E., Stinnesbeck, W., & González, A. H. G. 2006. A new thalattosuchian crocodyliform from the Tithonian (Upper Jurassic) of northeastern Mexico. Comptes Rendus Palevol, 5(6), 785-794. https://www.researchgate.net/publication/257564988_A_new_specimen_of_Cricosaurus_saltillensis_Crocodylomorpha_Metriorhynchidae_from_the_Upper_Jurassic_of_Mexico_evidence_for_craniofacial_convergence_within_MetriorhynchidaeBuchy, M. C., Young, M. T., & Andrade, M. B. 2013. A new specimen of Cricosaurus saltillensis (Crocodylomorpha: Metriorhynchidae) from the Upper Jurassic of Mexico: evidence for craniofacial convergence within Metriorhynchidae. Oryctos, 10, 9-21. https://doi.org/10.1016/j.crpv.2006.03.003 and Pimienta Formations).Frey, E., Buchy, M.-C., Stinnesbeck, W. & López-Oliva, J.G. 2002. ''Geosaurus vignaudi'' n. sp. (Crocodylia, Thalattosuchia), first evidence of metriorhynchid crocodilians in the Late Jurassic (Tithonian) of central-east Mexico (State of Puebla). ''Canadian Journal of Earth Sciences'' 39: 1467–1483. and from the earliest Cretaceous (lower

Berriasian In the geological timescale, the Berriasian is an age/ stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 143.1 ±0.6 Ma and 137.05 ± 0.2 (million years ago) ...

) of Argentina. ''C. schroederi'' from Valanginian of Germany is later reclassified to ''

Enalioetes ''Enalioetes'' is an extinct genus of metriorhynchid thalattosuchian from the Early Cretaceous Stadthagen Formation of Germany. The type species is ''E. schroederi''. Prior to its description in 2024, it was known under the informal names '' E ...

''.

Classification

The original three skulls (all assigned to different species) were poorly known, and the genus had been considered a

junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

of ''

Metriorhynchus ''Metriorhynchus'' is an extinct genus of marine crocodyliform that lived in the oceans during the Late Jurassic. The type species, ''M. brevirostris'' was named in 1829 as a species of ''Steneosaurus'' before being named as a separate genus by ...

'', ''

Geosaurus ''Geosaurus'' is an extinct genus of marine crocodyliform within the family Metriorhynchidae, that lived during the Late Jurassic and the Early Cretaceous. ''Geosaurus'' was a carnivore that spent much, if not all, its life out at sea. No ''Geosa ...

'' or ''

Dakosaurus ''Dakosaurus'' is an extinct genus of crocodylomorph within the family Metriorhynchidae that lived during the Late Jurassic and Early Cretaceous. It was large, with teeth that were serrated and compressed lateromedially (flattened from side to s ...

'' by different palaeontologists in the past.Steel R. 1973. ''Crocodylia. Handbuch der Paläoherpetologie, Teil 16''. Stuttgart: Gustav Fischer Verlag, 116 pp. Some

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analysis did not support the

monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...

of ''Cricosaurus'',Young MT. 2007. The evolution and interrelationships of Metriorhynchidae (Crocodyliformes, Thalattosuchia). ''Journal of Vertebrate Paleontology'' 27 (3): 170A. However, a more comprehensive analysis in 2009 showed that the species contained in ''Cricosaurus'' were valid, and furthermore that several long-snouted species formerly classified in the related genera ''Geosaurus'', ''Enaliosuchus'' and ''Metriorhynchus'' were in fact more closely related to the original specimens of ''Cricosaurus'', and thus were re-classified into this genus.Young, M.T. and de Andrade, M.B. (2009). "What is ''Geosaurus''? Redescription of ''Geosaurus giganteus'' (Thalattosuchia: Metriorhynchidae) from the Upper Jurassic of Bayern, Germany." ''Zoological Journal of the Linnean Society'', 157: 551-585.

Cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

after Young ''et al.'' (2020). Cricosaurus bambergensis 455445

Cladogram after Sachs ''et al.'' (2021):Sven Sachs, Mark Thomas Young, Pascal Abel, Heinrich Mallison (2021). A new species of ''Cricosaurus'' (Thalattosuchia, Metriorhynchidae) based upon a remarkably well-preserved skeleton from the Upper Jurassic of Germany. ''Palaeontologia Electronica'', 24.2.a24. DOI: 10.26879/928

Paleobiology

All currently known species would have been three metres or less in length. When compared to living crocodilians, ''Cricosaurus'' can be considered moderate to small-sized. Its body was streamlined for greater hydrodynamic efficiency, which along with its finned tail made it a more efficient swimmer than modern crocodilian species.Massare JA. 1988. Swimming capabilities of Mesozoic marine reptiles; implications for method of predation. ''Paleobiology'' 14 (2):187-205.

Salt glands

Recent examination of the fossil specimens of ''Cricosaurus araucanensis'' have shown that both juveniles and adults of this species had well-developed

salt gland The salt gland is an organ (anatomy), organ for excreting excess salt (chemistry), salts. It is found in the cartilaginous fishes subclass elasmobranchii (sharks, rays, and skates), seabirds, and some reptiles. Salt glands can be found in the r ...

s. This means that it would have been able to "drink" salt-water from birth (necessary for a

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

animal) and eat prey that have the same ionic concentration as the surrounding sea water (i.e.

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

s) without dehydrating.Fernández M, Gasparini Z. 2000. Salt glands in a Tithonian metriorhynchid crocodyliform and their physiological significance. ''Lethaia'' 33: 269-276.Fernández M, Gasparini Z. 2008. Salt glands in the Jurassic metriorhynchid ''Geosaurus'': implications for the evolution of osmoregulation in Mesozoic crocodyliforms. ''Naturwissenschaften'' 95: 79-84. Adult specimens of ''

'' also have these well-developed salt glands.Gandola R, Buffetaut E, Monaghan N, Dyke G. 2006. Salt glands in the fossil crocodile ''Metriorhynchus''. ''Journal of Vertebrate Paleontology'' 26 (4): 1009-1010.

Niche partitioning

Several species of metriorhynchids are known from the Mörnsheim Formation (

Solnhofen limestone The Solnhofen Limestone or Solnhofen Plattenkalk, formally known as the Altmühltal Formation, is a Jurassic Konservat-Lagerstätte that preserves a rare assemblage of fossilized organisms, including highly detailed imprints of soft bodied organi ...

, early Tithonian) of

Bavaria Bavaria, officially the Free State of Bavaria, is a States of Germany, state in the southeast of Germany. With an area of , it is the list of German states by area, largest German state by land area, comprising approximately 1/5 of the total l ...

, Germany: ''Cricosaurus suevicus'', '' Dakosaurus maximus'', ''

Geosaurus giganteus ''Geosaurus'' is an extinct genus of marine crocodyliform within the family Metriorhynchidae, that lived during the Late Jurassic and the Early Cretaceous. ''Geosaurus'' was a carnivore that spent much, if not all, its life out at sea. No ''Geosa ...

'' and '' Rhacheosaurus gracilis''. It has been hypothesised that

niche partitioning In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for e ...

enabled several species of crocodyliforms to co-exist. The top predators of this Formation appear to be ''D. maximus'' and ''G. giganteus'', which were large, short-snouted species with serrated teeth. The long-snouted ''C. suevicus'' and ''R. gracilis'' would have fed mostly on fish, although the more lightly built ''Rhacheosaurus'' may have specialised towards feeding on small prey. In addition to these four species of metriorhynchids, a moderate-sized species of ''

'' was also contemporaneous.Andrade MB, Young MT. 2008
High diversity of thalattosuchian crocodylians and the niche partition in the Solnhofen Sea
. The 56th Symposium of Vertebrate Palaeontology and Comparative Anatomy From the Nusplingen Plattenkalk (early Tithonian) of southern Germany, both ''C. suevicus'' and ''Dakosaurus maximus'' are contemporaneous. As with Solnhofen, ''C. suevicus'' feed upon fish, while ''D. maximus'' was the top predator.Dietl G, Dietl O, Schweigert G, Hugger R. 2000. ''Der Nusplinger Plattenkalk (Weißer Jura zeta)'' - Grabungskampagne 1999.

Possible viviparity

The hip of ''Cricosaurus araucanensis'' contains several features that create an unusually large pelvic opening. The

acetabulum The acetabulum (; : acetabula), also called the cotyloid cavity, is a wikt:concave, concave surface of the pelvis. The femur head, head of the femur meets with the pelvis at the acetabulum, forming the Hip#Articulation, hip joint. Structure The ...

, or

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

articulation on the hip, is placed very far towards of the bottom of the body relative to the vertebral column, and the sacral ribs are angled downwards at 45°, further increasing the distance between the vertebral column and the pubis-

ischium The ischium (; : is ...

. The hip was effectively a vertical ellipse in cross-section, being tall and wide. In other pseudosuchians like ''

'', ''

Machimosaurus ''Machimosaurus'' is an extinct genus of machimosaurid crocodyliform from the Late Jurassic (Kimmeridgian and Tithonian) and Early Cretaceous. The type species, ''Machimosaurus hugii'', was found in Switzerland. Other fossils have been found in ...

'', and ''

Pelagosaurus ''Pelagosaurus'' (meaning "lizard of the open sea") is an extinct genus of thalattosuchian crocodyliform that lived during the Toarcian stage of the Lower Jurassic, around 183 Ma to 176 Ma (million years ago), in shallow epicontinental seas t ...

'', the sacral ribs are less angled and more horizontal; in this way, ''Cricosaurus'' is actually more similar to aquatic reptiles like ''

Chaohusaurus ''Chaohusaurus'' is an extinct genus of basal ichthyosauriform, depending on definition possibly ichthyosaur, from the Early Triassic of Chaohu and Yuanan, China. Discovery and naming The type species ''Chaohusaurus geishanensis'' was name ...

'', ''

Utatsusaurus ''Utatsusaurus hataii'' is the earliest-known ichthyopterygian which lived in the Early Triassic period (c. 245–250 million years ago). It was nearly long with a slender body. The first specimen was found in Utatsu-cho (now part of Minamisa ...

'', and ''

Keichousaurus ''Keichousaurus'' (meaning " Kweichow lizard") is an extinct genus of pachypleurosaurian marine reptile from the Chialingchiang and Falang Formations of China with two known species attributed to the genus: ''K. hui'' and ''K. yuananensis''. ...

'', the latter of which live birth has been suggested for. In an evaluation of different reproductive hypotheses for ''Cricosaurus'' and other metriorhynchids, Herrera ''et al.'' considered

viviparity In animals, viviparity is development of the embryo inside the body of the mother, with the maternal circulation providing for the metabolic needs of the embryo's development, until the mother gives birth to a fully or partially developed juv ...

more likely than

oviparity Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...

References

External links

When Crocodiles Once Dived Like Dolphins and Whales
NY Times article on marine Thalattosuchian fossils, including Cricosaurus. Published April 20, 2020; Updated June 25, 2020 {{Taxonbar, from=Q147582 Thalattosuchia Prehistoric pseudosuchian genera Oxfordian genus first appearances Kimmeridgian genera Tithonian genera Valanginian genus extinctions Prehistoric marine crocodylomorphs Late Jurassic crocodylomorphs of Europe Fossils of France Jurassic Germany Fossils of Germany Solnhofen fauna Late Jurassic crocodylomorphs of North America Jurassic Cuba Fossils of Cuba Jurassic Mexico Fossils of Mexico Late Jurassic crocodylomorphs of South America Jurassic Argentina Fossils of Argentina Neuquén Basin Fossil taxa described in 1858 Taxa named by Johann Andreas Wagner Early Cretaceous crocodylomorphs of Europe Early Cretaceous crocodylomorphs of South America Berriasian genera Cretaceous Argentina Cretaceous Germany Jurassic France