Rhomaleosauridae

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Rhomaleosaurids
Temporal range: 201–161  Ma
Rhomaleosaurus cramptoni (fossil).jpg
Rhomaleosaurus cramptoni (NHMUK PV R.34), Natural History Museum
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder:† Sauropterygia
Order:† Plesiosauria
Family:† Rhomaleosauridae
Kuhn, 1961
Genera

Rhomaleosauridae is a family of plesiosaurs from the Earliest Jurassic to the latest Middle Jurassic (Hettangian to Callovian stages) of Europe, North America, South America and possibly Asia. Most rhomaleosaurids are known from England, many specifically from lower Blue Lias deposits that date back to the earliest Jurassic, just at the boundary with the Triassic. In fact, to date only two undisputed rhomaleosaurids were named from outside Europe - the closely related Borealonectes russelli and Maresaurus coccai from Canada and Argentina, respectively. These two species are also the only Middle Jurassic representatives of the family. [1] Rhomaleosauridae was formally named by Kuhn in 1961, originally proposed to include Rhomaleosaurus cramptoni and its relatives, which have short necks and large heads relatively to plesiosauroids like Elasmosaurus and Plesiosaurus , but longer necks and smaller heads relatively to advanced pliosaurids like Pliosaurus and Kronosaurus . [2]

Phylogeny

Rhomaleosauridae is a stem-based taxon defined in 2010 (and in earlier studies in a similar manner) as "all taxa more closely related to Meyerasaurus victor than to Leptocleidus superstes , Pliosaurus brachydeirus or Polycotylus latipinnis ". [2] Modern cladistic analyses are divided in the position of Rhomaleosauridae; some recover it at the base of Plesiosauria in a position basal to Neoplesiosauria that contains both the pliosauroids and the plesiosauroids, [3] while other analyses recover Rhomaleosauridae as pliosauroids, to the exclusion of Plesiosauroidea, either as the sister taxon of Pliosauridae or, rarely, as a paraphyletic array of taxa leading to it. [4] [2] Additionally, many putative rhomaleosaurids from the early deposits of Blue Lias, vary greatly in their position across various phylogenetic analyses. Some of these are recovered as basal rhomaleosaurids in certain analyses, or alternatively outside Rhomaleosauridae in more basal positions within Plesiosauria. [4] [2] [3] [1] The following two cladograms are simplified after two recent analyses, showing only the relationships within Rhomaleosauridae, and some other relevant basal taxa whose position within the family is highly uncertain.

Following Benson et al. (2012): [3]

Plesiosauria  
Cast of Plesiosaurus macrocephalus, a possible rhomaleosaurid, and perhaps a juvenile of Thaumatodracon Macrocephalus.jpg
Cast of Plesiosaurus macrocephalus , a possible rhomaleosaurid, and perhaps a juvenile of Thaumatodracon

Following Benson & Druckenmiller (2014), with Macroplata and Eurycleidus excluded, and Borealonectes added: [1]

Plesiosauria  

Related Research Articles

<span class="mw-page-title-main">Plesiosauroidea</span> Extinct clade of reptiles

Plesiosauroidea is an extinct clade of carnivorous marine reptiles. They have the snake-like longest neck to body ratio of any reptile. Plesiosauroids are known from the Jurassic and Cretaceous periods. After their discovery, some plesiosauroids were said to have resembled "a snake threaded through the shell of a turtle", although they had no shell.

<span class="mw-page-title-main">Pliosauroidea</span> Extinct clade of reptiles

Pliosauroidea is an extinct clade of plesiosaurs, known from the earliest Jurassic to early Late Cretaceous. They are best known for the subclade Thalassophonea, which contained crocodile-like short-necked forms with large heads and massive toothed jaws, commonly known as pliosaurs. More primitive non-thalassophonean pliosauroids resembled plesiosaurs in possessing relatively long necks and smaller heads. They originally included only members of the family Pliosauridae, of the order Plesiosauria, but several other genera and families are now also included, the number and details of which vary according to the classification used.

<span class="mw-page-title-main">Elasmosauridae</span> Extinct family of reptiles

Elasmosauridae is an extinct family of plesiosaurs, often called elasmosaurs. They had the longest necks of the plesiosaurs and existed from the Hauterivian to the Maastrichtian stages of the Cretaceous, and represented one of the two groups of plesiosaurs present at the end of the Cretaceous alongside Polycotylidae.

<i>Rhomaleosaurus</i> Genus of rhomaleosaurid plesiosaur from the Early Jurassic period

Rhomaleosaurus is an extinct genus of Early Jurassic rhomaleosaurid pliosauroid known from Northamptonshire and from Yorkshire of the United Kingdom. It was first named by Harry Seeley in 1874 and the type species is Rhomaleosaurus cramptoni. It was one of the earliest large marine reptile predators which hunted in the seas of Mesozoic era, measuring about 7 metres (23 ft) long. Like other pliosaurs, Rhomaleosaurus fed on ichthyosaurs, ammonites and other plesiosaurs.

<i>Umoonasaurus</i> Extinct species of reptile

Umoonasaurus is an extinct genus of plesiosaur belonging to the family Leptocleididae. This genus lived approximately 115 million years ago during the Early Cretaceous period, in shallow seas covering parts of what is now Australia. It was a relatively small animal around 2.5 metres (8.2 ft) long. An identifying trait of Umoonasaurus is three crest-ridges on its skull.

<span class="mw-page-title-main">Pliosauridae</span> Extinct family of reptiles

Pliosauridae is a family of plesiosaurian marine reptiles from the Latest Triassic to the early Late Cretaceous of Australia, Europe, North America and South America. The family is more inclusive than the archetypal short-necked large headed species that are placed in the subclade Thalassophonea, with basal forms resembling other plesiosaurs with long necks. They became extinct during the early Late Cretaceous and were subsequently replaced by the mosasaurs. It was formally named by Harry G. Seeley in 1874.

<i>Leptocleidus</i> Extinct genus of reptiles

Leptocleidus is an extinct genus of plesiosaur, belonging to the family Leptocleididae. It was a small plesiosaur, measuring only up to 3 m (9.8 ft).

Maresaurus is an extinct genus of plesiosaur from the Middle Jurassic (Bajocian) Los Molles Formation of Argentina. The type species, Maresaurus coccai, was named by Gasparini in 1997. Recent phylogenetic analysis found Maresaurus to be a rhomaleosaurid.

<span class="mw-page-title-main">Leptocleididae</span> Extinct family of reptiles

Leptocleididae is a family of small-sized plesiosaurs that lived during the Early Cretaceous period. They had small bodies with small heads and short necks. Leptocleidus and Umoonasaurus had round bodies and triangle-shaped heads. Leptocleidids have been found in what were shallow nearshore, freshwater and brackish habitats. Hilary F. Ketchum and Roger B. J. Benson (2010), transferred Brancasaurus, Kaiwhekea, Nichollssaura and Thililua to this family. However, Ketchum and Benson (2011) reassigned Kaiwhekea and Thililua to their original positions, as an elasmosaurid and a polycotylid, respectively.

<i>Hauffiosaurus</i> Extinct genus of reptiles

Hauffiosaurus is an extinct genus of Early Jurassic pliosaurid plesiosaur known from Holzmaden of Germany and from Yorkshire of the United Kingdom. It was first named by Frank Robin O’Keefe in 2001 and the type species is Hauffiosaurus zanoni. In 2011, two additional species were assigned to this genus: H. longirostris and H. tomistomimus.

Eurycleidus is an extinct genus of large-bodied rhomaleosaurid known from the Early Jurassic period of the United Kingdom. It contains a single species, E. arcuatus. Like other plesiosaurs, Eurycleidus probably lived on a diet of fish, using its sharp needle-like teeth to catch prey. Its shoulder bones were fairly large, indicating a powerful forward stroke for fast swimming.

<i>Meyerasaurus</i> Extinct genus of reptiles

Meyerasaurus is an extinct genus of rhomaleosaurid known from Holzmaden, Baden-Württemberg of southwestern Germany.

<i>Avalonnectes</i> Extinct genus of reptiles

Avalonnectes is an extinct genus of small-bodied rhomaleosaurid known from the Early Jurassic period of the United Kingdom. It contains a single species, A. arturi.

<i>Stratesaurus</i> Extinct genus of reptiles

Stratesaurus is an extinct genus of small-bodied rhomaleosaurid plesiosaur known from the Early Jurassic period of the United Kingdom. It contains a single species, S. taylori. It was a small plesiosaur, with a skull length of 18 cm (7.1 in) and a body length of 2 m (6.6 ft).

<i>Eoplesiosaurus</i> Extinct genus of reptiles

Eoplesiosaurus is an extinct genus of basal plesiosauroid known from the Early Jurassic period of the United Kingdom. It contains a single species, E. antiquior.

<span class="mw-page-title-main">Microcleididae</span> Extinct family of reptiles

Microcleididae is an extinct family of basal plesiosauroid plesiosaurs from the Early Jurassic of France, Germany, Portugal and the United Kingdom. Currently, the oldest and the most known microcleidid is Eretmosaurus from the middle Sinemurian of the United Kingdom. Microcleididae was formally named and described by Roger B. J. Benson, Mark Evans and Patrick S. Druckenmiller in 2012.

Spitrasaurus is an extinct genus of cryptoclidid plesiosauroid plesiosaur known from the uppermost Jurassic of central Spitsbergen, Norway and likely also Kimmeridge, England. It is named after a syllabic abbreviation for Spitsbergen Travel.

<i>Atychodracon</i> Extinct genus of reptiles

Atychodracon is an extinct genus of rhomaleosaurid plesiosaurian known from the Late Triassic - Early Jurassic boundary of England. It contains a single species, Atychodracon megacephalus, named in 1846 originally as a species of Plesiosaurus. The holotype of "P." megacephalus was destroyed during a World War II air raid in 1940 and was later replaced with a neotype. The species had a very unstable taxonomic history, being referred to four different genera by various authors until a new genus name was created for it in 2015. Apart from the destroyed holotype and its three partial casts, a neotype and two additional individuals are currently referred to Atychodracon megacephalus, making it a relatively well represented rhomaleosaurid.

References

  1. 1 2 3 Benson, R. B. J.; Druckenmiller, P. S. (2013). "Faunal turnover of marine tetrapods during the Jurassic-Cretaceous transition". Biological Reviews. 89 (1): 1–23. doi:10.1111/brv.12038. PMID   23581455. S2CID   19710180.
  2. 1 2 3 4 Ketchum, H.F.; Benson, R.B.J. (2010). "Global interrelationships of Plesiosauria (Reptilia, Sauropterygia) and the pivotal role of taxon sampling in determining the outcome of phylogenetic analyses". Biological Reviews of the Cambridge Philosophical Society. 85 (2): 361–392. doi:10.1111/j.1469-185X.2009.00107.x. PMID   20002391. S2CID   12193439.
  3. 1 2 3 Roger B. J. Benson; Mark Evans; Patrick S. Druckenmiller (2012). "High Diversity, Low Disparity and Small Body Size in Plesiosaurs (Reptilia, Sauropterygia) from the Triassic–Jurassic Boundary". PLOS ONE. 7 (3): e31838. Bibcode:2012PLoSO...731838B. doi: 10.1371/journal.pone.0031838 . PMC   3306369 . PMID   22438869.
  4. 1 2 Adam S. Smith and Gareth J. Dyke (2008). "The skull of the giant predatory pliosaur Rhomaleosaurus cramptoni: implications for plesiosaur phylogenetics" (PDF). Naturwissenschaften. 95 (10): 975–980. Bibcode:2008NW.....95..975S. doi:10.1007/s00114-008-0402-z. PMID   18523747. S2CID   12528732.
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