Cetiosauriscus

*Cetiosauriscus stewarti*

***Cetiosauriscus*** (/siːθiːuːsɒrɪskʌs/ meaning "whale-lizard-like" i.e. "*Cetiosaurus*-like") is a genus of sauropod dinosaur. It was perhaps a diplodocid, a relative of *Diplodocus*, and lived in the Callovian (Middle to Late Jurassic Period) of England (about 165 to 161 million years ago [mya]). *Cetiosauriscus* was a quadrupedal, herbivorous, saurischian. It was named by Friedrich von Huene in 1927, the species name being *C. leedsi*. Later it was shown that *C. leedsi* was not a *Cetiosauriscus* species, so, in 1993, Alan J. Charig sent a petition to the ICZN to designate *C. stewarti* as the type species. The remains include a series of vertebra, a hind leg, a possible whiplash tail, a partial sacrum, and a front leg. Cetiosauriscus has, over time, been classified in Cardiodontinae within Cetiosauridae, Diplodocidae, and Mamenchisauridae. It lived alongside *Eustreptospondylus*, *Sarcolestes*, *Callovosaurus*, *Lexovisaurus*, and possibly *Megalosaurus*, and *Cetiosaurus*.

## History of discovery

*Cetiosauriscus* was first named by German palaeontologist Friedrich von Huene in 1927, from Early Callovian age remains, the specific name of the genus being *Cetiosauriscus leedsi*. Its generic name means "whale-like lizard (i.e. *Cetiosaurus*-like)". In 1887 John Whittaker Hulke had named the species *Ornithopsis leedsii*, based on specimen BMNH R.1984-1988, a set of bones from the Leeds collection. After a suggestion by Harry Govier Seeley, in 1905 this species was renamed to *Cetiosaurus leedsi* by Arthur Smith Woodward, who referred a second specimen from the same collection to the species: BMNH R.3078. The specimen was mounted for many years and was exhibited in the Dinosaur Gallery of the Natural History Museum in London. Both specimens were assigned to *Cetiosauriscus leedsi* by von Huene. In 1929 von Huene also renamed *Ornithopsis greppini*, a species found in Switzerland, *"Cetiosauriscus" greppini*.

In 1980 A.J. Charig concluded that BMNH R.3078 could not be referred to BMNH R.1984-1988, due to a lack of comparable bones, and created a new species for the former: *Cetiosauriscus stewarti*. The specific name honours Sir Ronald Stewart, the chairman of the London Brick Company which owned the clay pit the fossils had been found in. Furthermore he considered both *C. leedsi* and *"C." greppini* *nomina dubia*.

Phillips (1871) based *Cetiosaurus glymptonensis* on nine middle-distal caudal centra from the Forest Marble Formation of Oxfordshire, England. Upchurch and Martin (2003) reexamined this material and concluded that it was potentially a diplodocid and was distinct from both *Cetiosaurus oxoneinsis* and Cetiosauriscus. The centra are elongated, as occurs in many diplodocids. The lateral surfaces of the centra bear two parallel horizontal ridges, causing the centra to be octagonal in transverse cross-section. The upper ridge is also present in *Cetiosauriscus* but the lower ridge is unique. This was later renamed into *Cetiosauriscus*.

In 1990 John Stanton McIntosh renamed two more species of *Cetiosaurus* into *Cetiosauriscus*. They were Cetiosauriscus longus and *"Cetiosauriscus" glymptonensis*. Neither, however, was sufficiently complete to determine whether they possess the characteristic autapomorphy. Both were again considered nomina dubia by Charig, who, in 1993, petitioned the ICZN to make *Cetiosauriscus stewarti* the type species instead of the original *Cetiosauriscus leedsi*. This was done in 1995, making BMNH R.3078, already the holotype of the species *C. stewarti*, the genoholotype (holotype) of *Cetiosauriscus*.

BMNH R.3078 was found at Peterborough, Cambridgeshire, in strata of the Upper Oxford Clay and consists of a series of vertebrae from the rear half of the skeleton. Other remains, including a front leg with fossilized cartilage in its joint, a hind leg, a possible whiplash tail, and a partial sacrum have been referred to *C. stewarti*. With that much material, *Cetiosauriscus* is one of the most complete sauropods from the United Kingdom.

### Species

A few species have, over the years, been assigned to Cetiosauriscus. Only one is certainly referable to it though. Most species have been recombined from or into *Ornithopsis* or *Cetiosaurus*, historically a wastebasket taxon.

#### Valid species

In 1980, Charig named a mostly complete specimen previously identified as *Cetiosauriscus leedsi* into its own species, *Cetiosauriscus stewarti*. After *Cetiosauriscus leedsi*, the type species, was proven to not be a species of *Cetiosauriscus, Charig* sent a petition to the ICZN to identify *Cetiosauriscus stewarti* as the type species.[1] *Cetiosauriscus stewarti* is a possible senior synonym of *Cetiosauriscus leedsi*, *Cetiosaurus leedsi* and *Ornithopsis leedsi*.

* *Cetiosauriscus stewarti Charig*, 1980 (type) = *Cetiosauriscus leedsi*? (Hulke, 1887) Huene, 1927 (*nomen dubium*) = *Cetiosaurus leedsi*? (Hulke, 1887) Huene, 1932 (*nomen dubium*) = *Ornithopsis leedsi*? Hulke, 1887 (*nomen dubium*).

#### Invalid species

In 1927, von Huene recombined *Cetiosaurus leedsi* into *Cetiosauriscus* as *Cetiosauriscus leedsi*, the type species. *Cetiosaurus leedsi* was originally named by Hulke in 1887 as a species of *Ornithopsis*. The specimen BMNH R3706, including some ribs, may belong to a pliosaur but was originally noted as *Cetiosaurus leedsi*.[8] In 1905, Woodward moved it into the genus *Cetiosaurus*. These classifications are no longer accepted and *Ornithopsis leedsi* is thought to be an indeterminate Brachiosaurid. *Cetiosauriscus leedsi* is a possible junior synonym of *Cetiosauriscus stewarti*. Two years later, in 1929, von Huene renamed another species of *Ornithopsis* as a *Cetiosauriscus* species, *Cetiosauriscus greppini*. *"Cetiosauriscus" greppini* was later renamed *Cetiosaurus greppini* by von Huene in 1932, a junior synonym of *"Cetiosauriscus" greppini*. *"Cetiosauriscus" greppini* is from the Reuchenette Formation, a formation of Early Kimmeridgian age. It is known from three individuals, the holotype being the most complete. *"Cetiosauriscus" greppini* differs from *Cetiosauriscus stewarti* by having caudal transverse processes that are anteroposteriorly flat and have a distinct dorsal wing-like expansion. It also differs in having anterior posterior centrodiapophyseal laminae situated ventrally from the anterior caudal transverse process, a coracoid with a rounded outline and with a notch ventrally to the glenoid articular face, remarkably straight shafts of humerus and femur, a distal end of the humerus with a higher medial than lateral hemicondyle, a more proximally placed 4th trochanter, and a longer and straighter ischium shaft. These characters certify that both taxa differ on the generic level. The discovery of cartilaginous tissue relatively proximal to the end of the humerus of *"Cetiosauriscus" greppini* has suggested that the cartilage caps of sauropods may have been larger than predicted by an Alligator CCF and that the cartilage caps extended fairly far onto the metaphysics of some long bones. *"Cetiosauriscus" greppini* is now considered to be Eusauropoda incertae sedis. *Cetiosaurus longus*, in 1990, was recombined as a species of *Cetiosauriscus*, *Cetiosauriscus longus* by McIntosh. This classification is not accepted and *Cetiosauriscus longus* is a junior objective synonym of *Cetiosaurus longus* because it cannot be proven to possess any characteristic autapomorphies. In the same year, McIntosh also renamed *Cetiosaurus glymptonensis* as *"Cetiosauriscus" glymptonensis*. *"Cetiosauriscus" glymptonensis* is considered to be Eusauropoda incertae sedis, in need of a new genus.

*"Cetiosauriscus" greppini* is known from a femur with bite marks on it. The marks strongly match the teeth of Machimosaurus, meaning that Machimosaurus scavenged or possibly regularly preyed on animals like *Cetiosauriscus*. *"Cetiosauriscus" glymptonensis* is diagnosed by middle-distal caudal centra having a distinct horizontal ridge approximately one-third the way up the lateral surface.

* *Cetiosauriscus leedsi* (Hulke, 1887) Huene, 1927 (*nomen dubium*) = *Ornithopsis leedsi* Hulke, 1887 (*nomen dubium*) = *Cetiosaurus leedsi* (Hulke, 1887) Woodward, 1905 (*nomen dubium*) = *Cetiosauriscus stewarti*? Charig, 1980
* *"Cetiosauriscus" greppini* (Huene, 1922) Huene, 1929 (*nomen dubium*) = *Ornithopsis greppini* Huene, 1922 (*nomen dubium*) = *Cetiosaurus greppini* Huene, 1932 (*nomen dubium*) = non *Cetiosauriscus*
* *Cetiosauriscus longus* (Owen, 1842) McIntosh, 1990 (*nomen dubium*) = *Cetiosaurus longus* Owen, 1842 (*nomen dubium*)
* *"Cetiosauriscus" glymptonensis* (Phillips, 1871) McIntosh, 1990 = *Cetiosaurus glymptonensis* Phillips, 1871 (*nomen dubium*) = non *Cetiosauriscus*

## Description

*Cetiosauriscus* was a relatively small quadrupedal, herbivorous sauropod. It is estimated by Gregory S. Paul that *Cetiosauriscus* stood 6 m ft high and was 15 m ft in length, weighing about 4 ton. Another estimate, by Thomas R. Holtz Jr., had *Cetiosauriscus* standing up to 15 m ft long and weighing roughly 14 ton.

### Pelvis

The only overlapping material between BMNH R3078 and the holotype of *Cetiosauriscus leedsi* was an ilium. In both specimens the ilium was preserved in insufficient ways. Since the only overlapping material was impossible to compare, Charig found that BMNH R3078 was of a different species and he named it *Cetiosauriscus stewarti*.

### Vertebrae

Huene felt the vertebrae of BMNH R3078 had proportions different enough from *Cetiosaurus* to warrant its own genus. Also, the fusion of centra with minimal osseous proliferation is manifest in the caudal vertebrae of *Cetiosauriscus*. The *Cetiosaurus* specimen OUMNH J13695 has a low horizontal ridge on each of its lateral surfaces, creating a slightly subhexagonal tranverse cross-section, and is also seen on *Cetiosauriscus*, as well as the anterior caudals of *Haplocanthosaurus*, and caudals 15 to 30 of *Omeisaurus*. Also, the area around the periphery of each articular face is flattened, creating a 'bevelled' appearance, and also occurs in *Cetiosaurus* and *Haplocanthosaurus*. A whiplash tail was apparently found in the same deposits but it is not certain it belongs to the same individual. Since there is no overlapping material, this assignment to *Cetiosauriscus* should be treated with caution.

### Limbs

Since the proportions of the limbs in BMNH R3078 differed enough from *Cetiosaurus*, Huene found that it warranted a new genus. Metacarpal 1 is short and massive, with the prominent process on the lower part of the posterior margin of the lateral face, a characteristic of the diplodocoids *Diplodocus*, *Apatosaurus*, *Cetiosauriscus* and *Dicraeosaurus*.

### Distinguishing characteristics

A characteristic that distinguishes *Cetiosauriscus* is that it has axially concave summits on the cranial and middle caudal neural spines. *Barosaurus* differs from it in having a more complex sculpting laterally and ventrally in the caudals; in having a larger humerus-femur ratio; and in having differently developed chevrons.

## Classification

Cetiosauriscus was originally classified by Huene as a genus in the family Cetiosauridae, within the subfamily Cardiodontidae. The subfamily, including the other taxa Cetiosaurus, Haplocanthosaurus, Dystrophaeus, Elosaurus and Rhoetosaurus, was founded upon the general basal features of elongate cervicals and shortened dorsals—both opisthocoelous, amphicoelous caudals that are rod-shaped distally, paired sternal plates, an ilium lacking the postacetabular process (region of the ilium behind the ischium joint and acetabulum), a very wide pubis, wide distal ischium, significantly shorter forelimb than hindlimb, fibula lacking the middle muscle attachment, and long metacarpals and short metatarsals. This classification was amended in 1932 when Huene concluded Cetiosauriscus was closer to Haplocanthosaurus than Cetiosaurus in the family, because of forelimb and hindlimb proportions. Conversely, in 1956, Alfred Romer synonymised Cetiosauriscus and Cetiosaurus, a position that has not been followed by subsequent studies on the taxon.

David S. Berman and McIntosh in 1978 referred Cetiosauriscus to the family Diplodocidae along with multiple other genera; Diplodocus, Apatosaurus, Barosaurus, Mamenchisaurus Dicraeosaurus and Nemegtosaurus. Like other members of the family, Cetiosauriscus possesses wing-like transverse processes, divided chevrons with forward and backward projections, the tail is "whiplash"-like, the humerus is 2/3 the length of the femur, the calcaneum is absent, metatarsal III and IV are the longest, and metatarsal I has a process on the bottom back corner. This referral would make Cetiosauriscus, known from the Callovian, the oldest diplodocid, millions of years older than Diplodocus, Barosaurus or Apatosaurus. In the paper naming Cetiosauriscus stewarti, Charig also described the chevrons of a new specimen and created the term "diplodociform" to describe them. This meant they were robust and double-beamed, as in Diplodocus and its relatives like Mamenchisaurus. Because of the similarly "diplodociform" chevrons, Charig referred Cetiosauriscus to the Diplodocidae along with the new specimen. Elaborating upon his earlier paper, McIntosh (1990) weakly referred Cetiosauriscus to the subfamily Diplodocinae, characterised by more cervicals and fewer dorsals, tall sacrum neural spines, short forelimbs, no calcaneum, metatarsals III and IV being the longest, and a small process on the distal end of metatarsal I. The subfamily also included Diplodocus, Barosaurus and Apatosaurus. In 2004 this placement was followed by Weishampel et al. without comment.

A phylogenetic analysis of Cetiosauriscus was conducted in 2003 by Julia Heathcote and Upchurch, based upon the two most inclusive matrices of the time, those of Jeffrey A. Wilson (2002) and Upchurch (1995), neither of which had included the taxon in the past. Added to the analysis of Upchurch, Cetiosauriscus placed as the sister taxon of Tehuelchesaurus, in a group including Mamenchisaurus, Omeisaurus and Euhelopus, and a placement within a group of Omeisaurus and Mamenchisaurus was also found by using the Wilson matrix. Based on these two results, Heathcote and Upchurch concluded Cetiosauriscus was not a diplodocid or even within Diplodocoidea, instead being a more basal sauropod outside Neosauropoda. The phylogenetic analysis of Rauhut et al. (2005) resolved Cetiosauriscus in a clade with Omeisaurus, itself in a group with Losillasaurus and Mamenchisaurus, outside of Neosauropoda. The phylogenetic relationships of Cetiosauriscus were also tested in 2015 by Tschopp et al., as a potential diplodocid. Although the genus was found to be within Diplodocimorpha with one analysis method, it was also found outside Neosauropoda. In both, Cetiosauriscus stewarti was found to be in a clade alone with Barosaurus affinis, a dubious species known only from foot bones. Tschopp et al. concluded that Cetiosauriscus was not a diplodocid or a diplodocoid, as forcing it to be outside Neosauropoda was more parsimonious than forcing it to be within Diplodocoidea in all analyses. As the paper was only to test relationships within Diplodocidae, more solid conclusions regarding the position of Cetiosauriscus could not be made. The results of the favoured cladogram of Tschopp et al. is shown below:

## Paleobiology

### Palaeopathology

The series of distal caudal vertebrae NHMUK R1967, once referred to Cetiosauriscus, is similar to the caudals of Diplodocus, with two convex ends (biconvex) and a long and thin centrum. These caudals display signs of injury at two points along the series of ten vertebrae, where there are signs of breakage that was later healed. These lesions were identified as the same form of pathologies as found on the tail of Diplodocus. It has been suggested that the biconvex distal caudal vertebrae in sauropods were used for making whip-like cracking noise, being thin and delicate and not intended for impact, as the joints would be very vulnerable to damage rendering them useless.

### Palaeoecology

Cetiosauriscus lived during the Callovian, an epoch in the Middle Jurassic, about 166 to 164 mya. The single specimen is known from the Lower Member of the Oxford Clay Formation, along with multiple other dinosaur genera and many other groups of animals, in the biozone of the index fossil Kosmoceras jason. The Oxford Clay Formation is a marine deposit of southern and middle England, known for the high-quality preservation of some fossils and the large diversity of taxa. Sediments are generally brownish-grey mudstone, organic-rich with plentiful crushed ammonites and bivalves, at most 65 m (213 ft) thick. A large diversity of flora can be seen, preserved in the form of pollen and spores. Gymnosperms are present, along with pteridophytes, unidentifiable wood fragments, other intermediate pollen, and miscellaneous organic plant material.

The intermediate sauropod Ornithopsis leedsi is known from the same section of the formation as Cetiosauriscus, along with the stegosaurids Lexovisaurus durobrivensis and Loricatosaurus priscus (which are possibly synonyms), the basal ankylosaur Sarcolestes leedsi, the ornithopod Callovosaurus leedsi, and a second unnamed ornithopod taxon. Dinosaur eggs that have not yet been assigned to a taxon are also known from the Lower Oxford Clay. The theropods Eustreptospondylus and possibly Megalosaurus are also known from the Oxford Clay Formation, but slightly younger deposits (the Middle Member). In addition, the theropod Metriacanthosaurus is from an unknown level and age in the formation.

Hundreds of invertebrates are known from the marine deposits, including bivalves, gastropods, scaphopods, ammonites, teuthoids, a nautiloid, foraminifera, coelenterates, bryozoans, brachiopods, annelids, crustaceans, ostracods, cirripedes and echinoderms. Fish are known from the clades Elasmobranchii, Chimaera, and Actinopterygii, and the ichthyosaur Ophthalmosaurus, the plesiosaurs Cryptoclidus, Muraenosaurus, Tricleidus, Liopleurodon, Peloneustes, Pliosaurus and Simolestes, the crocodilians Metriorhynchus and Steneosaurus, and the pterosaur Rhamphorhynchus were all present.

## JPInstitute.com Description

Cetiosauriscus is a large, long-necked dinosaur found in Europe. Discovered over 100 years ago, there is still a question as to which family of dinosaurs it belongs. This large plant-eater could have been related to either the North American Diplodocus or the Asian Mamenchisaurus. Since Europe was about in the middle of these two continents, perhaps it was related to both!

Adding to the mystery of this dinosaur, no skull material has yet been found with any of the five partial skeletons discovered to date. It has gone through several name changes and there are currently four species attributed to the genus, spanning more than 20 million years of the Jurassic. It is expected that it will be studied and possibly reassigned in the future.

## Links

https://web.archive.org/web/20020628124621fw\_/http://www.jpinstitute.com/dinopedia/dinocards/dfcetios.html

## References

1. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `charig`
2. ↑ 2.0 2.1 2.2 Cite error: Invalid `<ref>` tag; no text was provided for refs named `thedinosauria`
3. ↑ 3.0 3.1 Cite error: Invalid `<ref>` tag; no text was provided for refs named `farlow`
4. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `upchurch`
5. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `naish`
6. ↑ 6.0 6.1 Cite error: Invalid `<ref>` tag; no text was provided for refs named `thunderlizards`