Palæos:		Unit 210: Eureptilia
The Vertebrates		400: Euichthyosauria

Eureptilia: Euichthyosauria

REPTILOMORPHA
|--SYNAPSIDA
`--+--ANAPSIDA
   |
   Eureptilia
   |--Protorothyrididae
   `--Diapsida
      |--Araeoscelidans
      `--Neodiapsida
         |--Younginiformes
         `--+--Ichthyosauria
            |  |--Shastasauria
            |  `--Euichthyosauria
            |     |--Californosaurus
            |     `--Parvipelvia
            |        |--Temnodontosaurus
            |        |--Eurhinosauria
            |        `--Thunnosauria
            `--Sauria
               |
               |--LEPIDOSAUROMORPHA
               `--ARCHOSAUROMORPHA            

Taxa on this Page

1. Californosaurus X
2. Euichthyosauria X
3. Eurhinosauria X
4. Parvipelvia X
5. Temnodontosaurus X

The most basal of the euichthyosaurs is Californosaurus  Kuhn, 1934.  (Synonyms: Toretocnemus, Delphinosaurus).  Californosaurus is known from the Lower Hosselkus Limestone of California.  Although it is a Triassic species, it has the "fishy" appearance and medium size (3 m) of many Jurassic forms.  Californosaurus is distinguished by a smaller number of pre-sacral vertebrae (45 or 50) than is usual in ichthyosaurs, but each vertebra is somewhat elongate Camp (1980: 195), so it still has the normal body length.  The tail is sharply bent downwards, giving the animal a shark-like caudal (tail) fin; a characteristic of later ichthyosaurs.  The phalanges (finger and toe bones) are quite circular and widely spaced, giving a more rounded flipper.

By the Jurassic, at level of the Parvipelvia, many ichthyosaurs had developed very large eyes.  Temnodontosaurus, one of the most basal Jurassic forms, had some of the largest eyes (26 cm diameter), although this was at least partially a function of its very large size (9 m).  From this we may speculate that the one of the distinguishing features of the Jurassic ichthyosaurs was an ability to move off the continental shelves into deep water. Stomach contents of the same species confirm this suspicion. Although Temnodontosaurus had a reasonably varied diet, its menu seems to have been particularly strong in squid which are often found at considerable depth.  ATW020517. 

Another Early Jurassic group, the Eurhinosauria is harder to make sense of.  These ichthyosaurs evolved an upper jaw which was substantially longer than the lower jaw.  The overall appearance was thus of a swordfish.  The eurhinosaurs appear to have been designed for a very fast, pursuit mode of prey capture.  

Euichthyosauria: 

Range: Late Triassic to middle Cretaceous

Phylogeny: Merriamosauria: Shastasauria + *: Californosaurus + Parvipelvia.

Links: Phylogeny of the Ichthyopterygia.  ATW020517.

Californosaurus:  (= Toretocnemus, Delphinosaurus)

Range:  Late Triassic of North America

Phylogeny: Euichthyosauria: Parvipelvia + *.

Characters: ~3 m; somewhat elongated; 45-50 dorsal vertebrae, rib articulations as in shastasaurs [S97] (see also image); tail sharply down-turned, with possible semilunate caudal fin; phalanges circular & widely spaced, giving large, rounded flipper [C80].

Links: Paleontology and Geology Glossary: C; The Journal of Vertebrate Paleontology.  

References: Camp (1980) [C80]; Sander (1997) [S97]. ATW020517.

Parvipelvia: Hudsonelpidia, Suevoleviathan

Range: Late Triassic to mid-Cretaceous

Phylogeny: Euichthyosauria: Californosaurus + *: Temnodontosaurus + Eurhinosauria + Thunnosauria.

Characters: Jurassic ichthyosaurs and transitional forms with mosaic of Jurassic characters (large orbit, notched phalanges on digit I, short postorbital skull, etc). ATW020517.

Temnodontosaurus: (= Leptopterygius) T. platyodon, T. eurycephalus.  

Range: Late Triassic to Early Jurassic of Europe. [C97a]

Phylogeny: Parvipelvia: Eurhinosauria + Thunnosauria + *.

Characters: to 9 m; largest eye ever measured; long, narrow jaw; numerous large teeth set in a dental groove [M97]; fusiform body, triangular dorsal fin; fish-like caudal fin long, rather long, narrow paddles of approximately equal length; stomach contents indicate unspecialized diet, heavy in squid; viviparous.

Temnodontosaurus eurycephalus McGowan 1974
Sinemurian of Lower Lias, Lyme Regis, Dorset
 Known so far only from a single skull, this was a large, powerful animal with very short, deep jaws.  The teeth were large, well-spaced, and firmly anchored in the jaw by with bulbous roots.  These features indicate a powerful, crushing bite, similar to that of the large theropod dinosaurs. Clearly, this creature was a hunter of other reptiles, such as plesiosaurs and other ichthyosaurs. [M91] 

Temnodontosaurus platyodon (Conybeare) 1822
Sinemurian of Lower Lias, Lyme Regis, Dorset
Length 5 to 9 metres.   The largest and commonest of several species of Temnodontosaurs, often attaining a length of 9 metres, comparable to the giant Triassic ichthyosaurs.  T. platyodon represents a totally different evolutionary line and ecological role from the small, rounded Ichthyosaurus, more equivalent to the "sea-serpent"-like Ladinian (Mid-Triassic) Cymbospondylus.  Temnodontosaurus had a long, slender, robust body.  The fore- and hind-limbs are of approximately equal length, and quite narrow and paddle-shaped, with only three or four digits.  The snout is long, and armed with strong conical teeth, indicating relatively large prey.  The tail and dorsal (back) fins were probably relatively smaller than in Ichthyosaurus. [M91].

Leptopterygius burgundiae (Gaudry) 1892
Toarcian of Epsilon Lias of Wurttemberg, southern Germany
Length: 7 metres.  The largest of the Wurttemberg ichthyosaurs, mature individuals exceeding 7 metres in length.  Whereas the various species of Stenopterygius, with sizes of 2 to 4 metres, are closely comparable in size and probably also ecological habits to modern dolphins, the much larger Leptopterygius is comparable to the modern killer whale (Orcinus) .   The second-most common species, accounting for 18% of identified specimens, L. burgundiae has a long slender body, slender fore- and hind-fins, and a relatively large head.  It has certain features in common with the contemporary and incompletely known English L. acutirostris (average length 6.4 to 8 metres, maximum would be more), raising the question of whether or not these are actually the same species.  There is also a connection with the Hettangian T. platyodon, which is most probably the ancestor of L. burgundiae/acutirostris.

Leptopterygius disinteger von Huene 1926
Epsilon Lias of Wurttemberg, southern Germany
Length: 4.3 metres.

Image: from the Max Salas Gallery at Prehistorics Illustrated

Links: Preparing Mary the ichthyosaur at Charmouth Fossils; Paleontology and Geology Glossary: Te; Dinosaurs: Model & Collectible Pricelist (see image at right); marinhos.htm (Spanish); BBC News | SCI/TECH | Monster eyes from the deep; temnodon; Diets; Eyes; An overview of the Jurassic Cliffs in Dorset; ??? (Japanese); Untitled Document (T. risor is a juvenile of T. platyodon); ??????(????) (Japanese).   

References: Callaway (1997a) [C97a], McGowan (1991) [M91]; McGowan (1997) [M97]. ATW030104.

Eurhinosauria: Eurhinosaurus, Excalibosaurus, Leptonectes.

Range: 

Phylogeny: Parvipelvia: Temnodontosaurus + Thunnosauria + *.

Characters:  2-7 m; maxilla elongate and substantially longer than lower jaw; maxilla with teeth along entire length, but directed laterally (as in pristids?)

Excalibosaurus
Sinemurian of Lower Lias, Somerset
Discovered only in 1984, and named after the famous sword of King Arthur, this ichthyosaur is unusual in having a lower jaw only about three- quarters of the length of the upper, giving it a somewhat swordfish-like appearance.  It appears to be the ancestor of the Toarcian Eurhinosaurus.  [M95]. 

Eurhinosaurus huenei Swinton 1930
Toarcian of Epsilon Lias of Wurttemberg, southern Germany, and Bavaria
Length usually 3.4 to 4.1 metres, largest form just over 7 metres
One of the most bizarre of all the ichthyosaurs, Euhrhinosaurus had an upper jaw twice the length of the lower, giving it a resemblance to the modern swordfish (Xiphias), which it probably also resembled in habits.  The body is long and slender, the fore- fin longer than the hind, and both pairs, as well as the caudal or tail fin, had a high aspect ratio (i.e. they were long and narrow), indicating a rapid swimmer.  This was a fairly common species, amounting to some 18% of identified ichthyosaurs at Wurttemberg.  E. huenei is the only recognized species of this genus, but I would say that the similar but earlier and more primitive Excalibosaurus should belong here too.  

Links: Eurhinosaurus; eurhino (German); Charitable Trust Artifacts; Excalibosaurus; ¿¡¿ì¸®³ë»ç¿ì·ç½º (Korean); English.   

References: McGowan (1995) [M95]. ATW020517.

checked ATW050512