| Qaisracetus | |
|---|---|
 | |
| Drawing of basic outline ofQaisracetus. | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | †Protocetidae |
| Subfamily: | †Protocetinae |
| Genus: | †Qaisracetus Gingerich et al. 2001 |
| Species | |
Qaisracetus is an extinctprotocetidearly whale known from theEocene (Lutetian,48.6 to 40.4 million years ago) ofBaluchistan,Pakistan (31°00′N70°12′E / 31.0°N 70.2°E /31.0; 70.2, paleocoordinates12°24′N65°42′E / 12.4°N 65.7°E /12.4; 65.7).[1][2]
The genus is named after theQaisrani Baloch tribe which assisted Gingerich and his team during their field work.[3] "Qaisra" is also etymologically close to the royal title used in Persian and many Indo-European languages (e.g. Kaiser, Czar, Caesar).[3] The species is named for Muhammad Arif, former paleontologist at theGeological Survey of Pakistan who contributed significantly to archaeocete paleontology in Pakistan.[4]
Qaisracetus is known from a dozen specimens, all found in or near the type locality. Among them are several well-preserved elements, including a well-preserved skull, partial skulls and braincases, several vertebrae including an almost complete sacrum, a left innominate, ribs, and partial limb elements.[5]
Qaisracetus is smaller thanPappocetus andBabiacetus but larger thanIndocetus.[6]Qaisracetus arifi is almost as complete asRodhocetus kasranii, the most complete articulated skeleton of a protocetid, and they were similar in size: the latter had an estimated body weight of 620 kg (1,370 lb), compared to 590 kg (1,300 lb) for the former.[7]
Qaisracetus has a generalized protocetid skull with the externalnares located relatively anteriorly (above C1) and a relatively broad frontal shield. Therostrum is narrower inQaisracetus than inTakracetus.[6]
The four sacral vertebrae are only partially fused: the first two are solidly fused, the third is locked in place by rib-like processes (apleurapophysealsynchondrosis), while the fourth has a caudal (tail-like) morphology including two ventralschevron processes. The fusion between S1 and S2 distinguishedQaisracetus from other protocetids such asProtocetus,Rodhocetus,Gaviacetus,Natchitochia, andGeorgiacetus.Qaisracetus' vertebrae are notdense and thick like inEocetus.[8] In contrast toQaisracetus,Rodhocetus has a sacrum where none of the vertebrae have fused centra, which isderived to be a protocetid, butRodhocetus isprimitive in retaining pleurapophyseal connections between all sacral vertebrae. The sacral morphology ofRodhocetus andQaisracetus indicate protocetids represent a wide range of specializations, although which is ancestral to later whales is unclear.[7]
Because of similarities in itsdental microwear patterns to those of present-dayorcas andhyenas,Q. arifi is believed to have eaten other marine mammals.[9]
