Eotitanosuchidae is an extinct family of

biarmosuchia Biarmosuchians are an extinct clade of non-mammalian synapsids from the Permian. They are the most basal group of the therapsids. All of them were moderately-sized, lightly-built carnivores, intermediate in form between basal sphenacodont " pelyc ...

therapsid Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...

s. The Eotitanosuchidae were large predatory therapsids of the

Wordian In the geologic timescale, the Wordian is an age or stage of the Permian. It is the middle of three subdivisions of the Guadalupian Epoch or Series. The Wordian lasted between and million years ago (Ma). It was preceded by the Roadian and f ...

epoch. It was once considered to belong to a separate

infraorder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

of therapsids called Eotitanosuchia.

Characteristics

The Eotitanosuchians seem to be more advanced than the

Biarmosuchia Biarmosuchians are an extinct clade of non-mammalian synapsids from the Permian. They are the most basal group of the therapsids. All of them were moderately-sized, lightly-built carnivores, intermediate in form between basal sphenacodont " pelyc ...

in that the temporal opening behind the

eye socket In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is , of ...

—although small—is still somewhat larger than the biarmosuchians; it is expanded in the upper rear ( posterodorsal) margin, allowing the area of attachment of the adductor ( jaw closing) muscles to be visible from the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

(top) view looking down. The eotitanosuchian bite was stronger and more efficient than the biarmosuchian bite. For this reason, some paleontologists see the eotitanosuchids as transitional between the biarmosuchians and higher

s. It is at least as likely that features of a larger temporal opening—and hence increased muscle mass and

biting Biting is a common zoological behavior involving the active, rapid closing of the jaw around an object. This behavior is found in toothed animals such as mammals, reptiles, amphibians and fish, but can also exist in arthropods. Myocytic cont ...

power—evolved simultaneously among a number of early therapsid groups, due to the obvious advantages this adaptation conferred. One must be wary in applying

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

methodology to characteristics that are likely to evolve simultaneously among many competing lineages. In other respects the eotitanosuchians are quite primitive; they were the least modified in their jaw apparatus from their

sphenacodont Sphenacodontia is a stem-based clade of derived synapsids. It was defined by Amson and Laurin (2011) as "the largest clade that includes ''Haptodus baylei'', ''Haptodus garnettensis'' and '' Sphenacodon ferox'', but not ''Edaphosaurus pogonias' ...

ancestry.

References

The main groups of non-mammalian synapsids at Mikko's Phylogeny Archive

External links

at Palaeos Biarmosuchians Guadalupian extinctions Guadalupian first appearances Prehistoric therapsid families {{paleo-therapsid-stub