| Tylopoda | |
|---|---|
 | |
| Adromedary camel | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Suborder: | Tylopoda Illiger, 1811 |
| Families | |
Camelidae | |
Tylopoda (meaning "calloused foot")[1] is asuborder ofterrestrialherbivorouseven-toed ungulates belonging to theorderArtiodactyla. They are found in the wild in theirnative ranges ofSouth America andAsia, whileAustralian feral camels areintroduced. The group has a long fossil history inNorth America andEurasia. Tylopoda appeared during theEocene around 50 million years ago.
Tylopoda has only oneextant family,Camelidae, which includescamels,llamas,guanacos,alpacas andvicuñas. This group was much more diverse in the past, containing a number of extinctfamilies in addition to the ancestors of living camelids (see below).
Tylopoda was named by Illiger (1811) and consideredmonophyletic by Matthew (1908). It was treated as an unranked clade by Matthew (1908) and as a suborder by Carroll (1988), Ursing et al. (2000) and Whistler and Webb (2005). It was assigned toRuminantia by Matthew (1908); toArtiodactyla by Flower (1883) and Carroll (1988); toNeoselenodontia by Whistler and Webb (2005); and toCetartiodactyla by Ursing et al. (2000) and by Agnarsson and May-Collado (2008).[3][4][5]
The main problem with circumscription of Tylopoda is that the extensive fossil record of camel-like mammals has not yet been thoroughly examined from acladistic standpoint. Tylopoda is a highly distinctive lineage among theartiodactyls, but its exact relationships are somewhat elusive because the six living species are all closely related and can be considered "living fossils", the sole surviving lineage of a prehistorically wildly successfulradiation. More recent studies suggest that tylopods are not as closely related toruminants as traditionally believed, expressed incladogram form as:[6][7][8][9][10][11]
| Artiodactyla |
| ||||||||||||||||||||||||
Tylopoda areextremely conservative in their lifestyle and (like ruminants) seem to have occupied the sameecological niche since their origin over 40 million years ago. Thus, it seems that the previous assumption of a close relationship between Tylopoda and ruminants is simply because all other close relatives (whales,pigs etc.) are so divergent in their adaptations as to have obscured most indications of relationship, or at least those visible tophenetic analyses. However, the ratherbasal position that Tylopoda appears to have among theeven-toed ungulates and relatives means that the oldest members of this lineage are stillmorphologically very primitive and hard to distinguish from the ancestors of related lineages. The first major modern and comprehensive analysis of the problem (in 2009) supported this; while some taxa traditionally considered Tylopoda could be confirmed to belong to this suborder (and a few refuted), the delimitation of this group is still very much disputed despite (or because of) an extensive fossil record.[6]
The taxa currently assigned (with some reliability) to Tylopoda are:[6]
SuperfamilyCameloidea
Superfamily †Merycoidodontoidea (=Oreodontoidea)
Several additional prehistoric(cet)artiodactyl taxa are sometimes assigned to the Tylopoda, but other authors consider themincertae sedis or basal lineages among the (Cet)artiodactyla or as more closely related to other artiodactyl groups likeruminants:
Some studies have consideredProtoceratidae closely related to Tylopoda, but others have considered them more closely related to theruminants.[12]
Data related toTylopoda at Wikispecies.png)
_(white_background).jpg)
.jpg)
.jpg)