Cetiosauriscus

Source: Wikipedia, the free encyclopedia.
Not to be confused with the sauropod dinosaur Cetiosaurus.

Cetiosauriscus
Temporal range:
Ma
↓
Composite photograph showing Alfred Leeds standing next to the mounted arm and rear skeleton of Cetiosauriscus, from soon before 1905
Composite photo of the mounted holotype skeleton shortly before display in 1905
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: †Sauropodomorpha
Clade: †Sauropoda
Clade: †Gravisauria
Clade: †Eusauropoda
Genus: †Cetiosauriscus
von Huene, 1927[2]
Species:
†C. stewarti
Binomial name
†Cetiosauriscus stewarti

Cetiosauriscus (

Period) in what is now England. A herbivore, Cetiosauriscus had — by sauropod standards — a moderately long tail, and longer forelimbs, making them as long as its hindlimbs
. It has been estimated as about 15 m (49 ft) long and between 4 and 10 t (3.9 and 9.8 long tons; 4.4 and 11.0 short tons) in weight.

The only known

phylogenetic analysis published in 2003 instead found the species to belong to Mamenchisauridae, and followed by studies in 2005 and 2015 that found it outside Neosauropoda
, while not a mamenchisaurid proper.

Cetiosauriscus was found in the marine deposits of the

theropods Eustreptospondylus and Metriacanthosaurus
are known from the formation, although probably not from the same level as Cetiosauriscus.

History of discovery

Background

Cetiosaurus oxoniensis

The fossil later known as Cetiosauriscus was originally ascribed to the genus

palaeontologist Richard Owen, and one with a complicated history due to many unfounded referrals of species and specimens, involving almost all English sauropod specimens. The type species of Cetiosaurus has changed throughout history because of incomplete remains and the taxon's significance, and many aspects of its anatomy and relationships are still uncertain. Cetiosaurus was originally named to include C. medius, C. brevis, C. brachyurus and C. longus, which span from the Middle Jurassic to the Early Cretaceous of various localities across England. As none of these species are truly diagnostic, and Cetiosaurus is a historically and taxonomically important taxon, the more complete Middle Jurassic species C. oxoniensis named by geologist John Phillips in 1871 became the type species. C. glymptonensis was also named in the same publication by Phillips, but is less complete and of questionable validity.[4]

Ornithopsis hulkei

Another English taxon,

Atlantosauridae.[9][A] Lydekker's classification of the species was not supported by later authors like palaeontologist Arthur Smith Woodward in 1905, who followed Seeley's classification scheme.[10]

Discovery and naming

Map of Cambridgeshire, England showing the location of the fossil quarry Cetiosauriscus was found in, in the top left corner below Peterborough
Map of Cambridgeshire, England showing the location of the fossil quarry Cetiosauriscus was found in, in the top left corner below Peterborough
NPBCL pit No. 1
class=notpageimage|
Location of the fossil discovery: NPBCL pit No. 1 in Cambridgeshire, England

The sauropod fossil today known as Cetiosauriscus stewarti was discovered in May

accession number BMNH R3078 (now NHMUK R3078).[7]

Known elements of Cetiosauriscus

The amount of material made NHMUK R3078 the most complete sauropod specimen from the

camarasaurid (possibly referable to Cetiosauriscus[17]), making it the first sauropod skeleton mounted in the United Kingdom.[7]

NHMUK R3078 was referred in 1905 by Arthur Woodward to the species Cetiosaurus leedsii, as it was from the same geologic formation as other specimens that were assigned to C. leedsii.[10] Woodward also referred the dorsal vertebrae NHMUK R1984 and the tail tip NHMUK R1967 to the species.[7][10] In 1927, Huene briefly described the anatomy of the species C. leedsii, where he noted that it shared many similarities with Haplocanthosaurus and was most likely between Cetiosaurus proper and the former genus. For this reason, Huene proposed the new genus name Cetiosauriscus for the species.[2] To the genus he referred the specimens NHMUK R1984–R1988 and NHMUK R3078.[14]

Misassigned species

Drawing of a tail bone
Caudal vertebra of "Cetiosauriscus" longus (now Eusauropoda indet.) seen from in front, above, the side, and cross section

Huene (1927) assigned "Ornithopsis" greppini, which he had named in 1922, to the genus Cetiosauriscus. The known material, discovered in Late Jurassic (Kimmeridgian) deposits in the Reuchenette Formation of Switzerland, includes dorsal and caudal vertebrae, forelimb bones, and a hindlimb and partial pes, from at least two individuals.[18] The 53 cm (21 in) long humerus was built like Cetiosauriscus stewarti (C. leedsi of von Huene's 1927 usage), and the two species were originally distinguished from Cetiosaurus by having shorter dorsal vertebrae, a shorter forelimb, and a longer lower leg.[19] Similarities such as the anatomy of the caudal vertebrae were suggested by Christian Meyer and Basil Thüring in 2003 to support the referral of greppini to Cetiosauriscus.[18] However, Weishampel et al. (2004) and Whitlock (2011) considered "Cetiosauriscus" greppini to be Eusauropoda incertae sedis, while Hofer (2005) and Schwarz et al. (2007) concluded that "Cetiosauriscus" greppini represents an unnamed genus of basal eusauropod.[15][20][21][22] "Ornithopsis" greppini was finally named as the new genus Amanzia in 2020.[23]

The species Cetiosaurus longus, named in 1842 by Owen, was referred to the genus Cetiosauriscus without comment by sauropod palaeontologist John Stanton McIntosh in 1990.

centra (body of the vertebra), C. longus is not a diagnostic taxon. As it lacks any diagnostic features of Cetiosauriscus, the species should be referred to by its original designation, Cetiosaurus longus.[4]

Cetiosaurus glymptonensis, named on the basis of nine middle-distal caudal centra from the Forest Marble Formation of Oxfordshire, England, was referred to Cetiosauriscus by McIntosh in 1990. These caudal vertebrae were considered to be more elongate than those of Cetiosaurus oxoniensis, but caudal length proportions vary significantly throughout the tail and in different taxa, Apatosaurus, Diplodocus and Cetiosauriscus having similarly elongate caudal vertebrae.[4] The more anterior caudals have a large ridge two-thirds up the centrum and a smaller ridge one-third up. These ridges are similar to the middle caudals of Cetiosauriscus. Still, they are absent in caudals of the same size and proportions, and because of this difference the species was concluded to be separate from Cetiosauriscus by Upchurch and Martin in 2003.[4] "Cetiosaurus" glymptonensis is considered to be Eusauropoda incertae sedis by Upchurch and Martin (2003), Weishampel and colleagues (2004) and Whitlock (2011), and is in need of a new genus name because it has a single diagnostic feature, the lateral ridges.[4][15][20]

Drawing of arm bones
Forelimb of Cetiosauriscus in front and top views

In 1980, Charig described a specimen of indeterminate diplodocid from the Early Cretaceous of England, and re-examined the holotype of Cetiosauriscus leedsii to compare its characteristics. In this publication he confirmed that the ilium of the holotype of C. leedsii, NHMUK R1988, was too incomplete to be compared to the also incomplete ilium of the referred specimen NHMUK R3078. Because of the lack of overlap the referral of NHMUK R3078 to Cetiosauriscus leedsii was no longer verifiable, so Charig named the new species Cetiosauriscus stewarti for NHMUK R3078. The specific name was chosen to honour Sir Ronald Stewart, the chairman of the London Brick Company that owned the clay pit the fossils had been found in. Furthermore, Charig considered Cetiosauriscus leedsii and Cetiosauriscus greppini to be dubious taxa, making C. stewarti the only valid species within Cetiosauriscus.[1] Because of the invalidity of the type species C. leedsii, Charig made a petition to the International Code of Zoological Nomenclature (ICZN) in 1993 to designate Cetiosauriscus stewarti as the type species of its genus, being the taxon containing the specimen Huene had originally named the genus for and distinguished from Cetiosaurus, and also a taxonomically more stable name.[14] This was accepted by the ICZN in 1995, making Cetiosauriscus stewarti the type species of Cetiosauriscus.[25] The only specimen that can confidently be assigned to C. stewarti is the holotype NHMUK R3078, although it is possible that isolated teeth from the Oxford Clay could be from the taxon.[7][17]

Description

Light brown sauropod silhouette with a medium length neck, long tail and long limbs, shown beside two humans
A diagram showing the possible size of Cetiosauriscus compared to humans

Cetiosauriscus was a moderately sized, quadrupedal eusauropod. It had a moderately long tail, and relatively long arms making the shoulders level with the hips. Cetiosauriscus was approximately 15 m (49 ft) long based on the known skeleton, comparable to possible relatives like 16 m (52 ft) long Cetiosaurus, and 16.5 m (54 ft) long Patagosaurus.[26] The weight of Cetiosauriscus is less certain, depending on its phylogenetic placement. Restored as a diplodocid, Cetiosauriscus was estimated by Paul (2010[27]) as 4 t (3.9 long tons; 4.4 short tons), but restored as a cetiosaur it was estimated by Paul (2016[26]) as 10 t (9.8 long tons; 11 short tons).[26][27]

Vertebrae

Drawing of a back bone
Posterior dorsal vertebra in rear and side views

The dorsal vertebrae of NHMUK R3078 are incomplete or fragmentary. A partial anterior dorsal is known from a single centrum, which is about as long as wide, with a strong anterior articular ball (an

postzygapophyses.[10] This is unlike most diplodocoids where there are many laminar running along the length of the spines.[28] Four neural spines of the sacrum are preserved, three of which form a single plate and the fourth of which is separate, like in Diplodocus.[10][2]

Drawing of a tail bone
Fourth caudal vertebra in front and side views

Of the anterior four caudal vertebrae, the anteriormost two are highly incomplete. Both the short, but wider-than-tall, centra preserve traces of the sideways projections (

transverse processes) found in other vertebrae, which are very low on the sides compared to following caudals. The neural spines are very thin, thinning to a single ridge in front (the prespinal lamina), but having two spinopostzygapophyseal laminae like the dorsals. The fourth caudal is the most complete anterior caudal. The centrum is concave in front, but flat behind (amphiplatyan). There are no pleurocoels unlike the dorsals, and the transverse processes begin in the top half of the centrum. The centrum is 10 cm (3.9 in) long, 27 cm (11 in) tall and 28 cm (11 in) wide, with the total vertebra being 66 cm (26 in) tall. Anterior caudals of the Cetiosaurus leedsi specimen NHMUK R1984 are very similar to those of Cetiosauriscus, but the neural arches are not as tall in C. leedsi, and the transverse processes lack a prominent ridge along the top of them. Middle and posterior caudals from a nearly continuous series of 27 bones are well preserved in Cetiosauriscus. The later vertebrae are slightly more elongate than those in front, and slightly less concave in their anterior face. Moving towards the end of the tail the centra reduce in size and the transverse processes shrink until they are completely absent, with the neural spines becoming shorter, thinner, and more slanted. The seventh vertebrae of the series, at 45 cm (18 in) tall, is 18 cm (7.1 in) long, only one cm longer than the 21st of the same series that is 22.5 cm (8.9 in) tall.[10] A distinguishing characteristic of Cetiosauriscus is the presence of a front-to-back concavity on the top of the anterior and middle caudal neural spines.[15]

Appendicular skeleton

Drawing of a large limb bone
Femur of Cetiosauriscus in rear, top, and bottom views and cross sections

Cetiosauriscus preserves a single right scapula (shoulder blade), which is elongate and slender. The scapula is 96.5 cm (38.0 in) long and 17.5 cm (6.9 in) wide at the middle, making it very narrow.[10][29] The inner face is flat across, while the outer face is gently convex. There is no expansion of the far end of the blade. The bone thickens close to the humerus joint, where it also articulates with the coracoid. The coracoid is incomplete, but enough is preserved to show it is rectangular, and longer, at 35 cm (14 in), than it is wide—38 cm (15 in). A 94 cm (37 in) long humerus is known, and complete with minimal crushing. The bone is short and stout, with a robust crest for the deltoid muscle along the upper half of the bone.[10] The shape of the humerus is similar to the shortness of Neuquensaurus, although overall the forelimb is long, as in Diplodocus and Cetiosaurus, being 69% of the femur length.[29][15] The distal end is roughened for a large cartilage cap as found in some other eusauropods like "Cetiosauriscus" greppini.[18] The radius and ulna are broken, but complete they would have been 76 cm (30 in) long.[10]

The hindlimb of Cetiosauriscus is about 3⁄2 the length of the forelimb. Both ilia are very fragmentary, but the two sides supplement each other to give a reasonable idea of the proportions of the complete bone. The ilium is 1.02 m (3.3 ft) long, and has a long and slender pubic

gracile femoral morphology is shared with Amphicoelias, Shunosaurus, Ligabuesaurus and a specimen of Diplodocus, being more gracile than Cetiosaurus and most other eusauropods.[2][28] A prominent fourth trochanter is present, but the remaining shaft is very compressed. The tibia, fibula and pes are also preserved, but are fragmentary and disarticulated making comparisons difficult, the lower hindlimb being about 80 cm (31 in) upright.[10][29] The foot is similar to Diplodocus and Brontosaurus, where the first toes are large and clawed, and the outer ones are small and clawless. Metatarsal III is the longest, followed by metatarsal IV, II, V and I. Metatarsal I is the widest, and the width of the bones decreases numerically.[10]

Classification

Coloured drawing of a sauropod with a long neck reaching to eat from a tree
Life restoration of Cetiosauriscus as a eusauropod

Cetiosauriscus was originally classified by Huene as a genus in the

metatarsals.[2] 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.[29] Conversely, in 1956, Alfred Romer synonymised Cetiosauriscus and Cetiosaurus, a position that has not been followed by subsequent studies on the taxon.[1][30]

David S. Berman and McIntosh in

calcaneum is absent, metatarsal III and IV are the longest, and metatarsal I has a process on the bottom back corner.[31] 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.[1] Elaborating upon his earlier paper, McIntosh (1990[24]) 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.[24] In 2004 this placement was followed by Weishampel et al. without comment.[15]

A

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:[28]

Drawing of the known skeleton in a life pose
1905 drawing of the mounted skeleton of Cetiosauriscus
Eusauropoda

Shunosaurus lii

Spinophorosaurus nigerensis

Omeisaurus

Mamenchisaurus

Cetiosauriscus stewarti

Barosaurus affinis

Jobaria tiguidensis

Amphicoelias latus

Lourinhasaurus alenquerensis

Camarasaurus

Turiasaurus riodevensis

Losillasaurus giganteus

Brachiosaurus sp.

Diplodocoidea

Macronaria

Giraffatitan brancai

Brachiosaurus altithorax

Ligabuesaurus leanzai

Isisaurus colberti

Palaeobiology

Drawing of a very long and thin tail bone
Unpathologic distal caudal of Cetiosauriscus? specimen NHMUK R1967

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.[10] These lesions were identified as the same form of pathologies as found on the tail of Diplodocus.[35] 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.[36]

Palaeoecology

Oxford Clay Formation
environment

Cetiosauriscus lived during the Callovian, an

epoch in the Middle Jurassic, about 166 to 164 mya.[37]
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
Gymnosperms are present, along with pteridophytes, unidentifiable wood fragments, other intermediate pollen, and miscellaneous organic plant material.[39]

The intermediate sauropod

theropods Eustreptospondylus and possibly Megalosaurus are also known from the Oxford Clay Formation, but slightly younger deposits (the Middle Member).[15] In addition, the theropod Metriacanthosaurus is from an unknown level and age in the formation.[17]

Hundreds of

ichthyosaur Ophthalmosaurus, the plesiosaurs Cryptoclidus, Muraenosaurus, Tricleidus, Liopleurodon, Peloneustes, Pliosaurus and Simolestes, the crocodilians Metriorhynchus and Steneosaurus, and the pterosaur Rhamphorhynchus were all present.[17]

Notes

  1. objective synonym of the original spelling.[1]

References

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Further reading

External links

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