| Cardiodon | |
|---|---|
 | |
| Holotype tooth seen from two different angles (2–3), another tooth (4) and a close-up of the surface of the tooth (5) | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Turiasauria |
| Genus: | †Cardiodon Owen, 1841 |
| Species: | †C. rugulosus |
| Binomial name | |
| †Cardiodon rugulosus Owen, 1844 | |
| Synonyms | |
| |
Cardiodon (meaning "hearttooth", in reference to the shape) was a herbivorousgenus ofsauropoddinosaur, based on atooth from theMiddle Jurassic (lateBathonian)Forest Marble Formation ofWiltshire,England. Historically, it is very obscure and usually referred toCetiosaurus, but recent analyses suggest that it is a distinct genus, and possibly related toTuriasaurus.Cardiodon was the first sauropod genus named.[1]
Richard Owen named the genus for a now-lost tooth, part of the collection of naturalistJoseph Chaning Pearce, found nearBradford-on-Avon, but did not assign it aspecific name at the time. The generic name is derived from Greek καρδία,kardia, "heart", and ὀδών,odon, "tooth", in reference to its heart-shaped profile.[2] A few years later, in 1844, he added the specific namerugulosus, meaning "wrinkled" inLatin.[3]Cardiodon was the first sauropod given a formal name to, though Owen was at the time completely unaware of the sauropod nature of the find.
Within a few decades, he and others were viewingCardiodon as a possible synonym of his most well-known sauropod genus,Cetiosaurus.[4][5]Richard Lydekker formalized this view in a roundabout way in 1890, by assigningCetiosaurus oxoniensis toCardiodon on the basis of teeth fromOxfordshire associated with a skeleton ofC. oxoniensis.[6] He also added a second tooth (BMNH R1527) from theGreat Oolite nearCirencester,Gloucestershire.[6] More typically,Cardiodon has been assigned toCetiosaurus, sometimes as a separate speciesCetiosaurus rugulosus,[7] in spite of its priority.
In 2003,Paul Upchurch andJohn Martin, reviewingCetiosaurus, found that there is little evidence to assign theC. oxoniensis teeth to the skeleton, and the "C. oxoniensis" teeth differ from theCardiodon teeth (Cardiodon teeth are convex facing thetongue); therefore, they supportedCardiodon being retained as its own genus.[8] Upchurchet al. (2004) repeated this assessment, and found that though the teeth have no knownautapomorphies, they are those of aeusauropod.[9] More recently, Royo-Torreset al. (2006), in their description ofTuriasaurus, pointed outCardiodon as a possible relative to their new, giant sauropod, placing it in theTuriasauria.[10] Earlier,Cardiodon had been usually assigned to theCetiosauridae or a Cardiodontidae of its own.
The original tooth shows, as far as can be deduced from the surviving illustrations, the rare combination of being spatulate and having a convex inner side, though the convexity is slight. Its crown is short and wide, slightly curving to the inside. The outer side is strongly convexly curved from the front to the rear. On this side a shallow groove is present, running parallel to the rear edge. The crown tapers towards its tip. The edges have no denticles. The enamel shows the little wrinkles to which the specific name refers.[8]
As a sauropod,Cardiodon would have been a large,quadrupedalherbivore,[9] but because of the scanty remains, much more cannot be said.
