Table 1. Skeletal measurements (cm) of Maiacetus inuus compared to those of the previously known protocetids Artiocetus clavis and Rodhocetus balochistanensis, which are also from the early middle Eocene of Pakistan [3].
| Measurement | Artiocetus clavis | Rodhocetus balochistan-ensis | Maiacetus inuus | Maiacetus inuus | Maiacetus inuus |
| GSP-UM 3458 (Type) | GSP-UM 3485 (Type) | GSP-UM 3475a (Type, female) | GSP-UM 3551 (Male) | Male/female Ratio2 | |
| Cranial length | 57.5 | 56.0 | |||
| Cranial width | 44.0 | 27.0 | |||
| Tympanic bulla length | 6.5 | 6.1 | 6.6 | 1.09 | |
| Tympanic bulla width | 4.8 | 4.9 | 5.4 | 1.12 | |
| Mandibular foramen height | 6.0 | 7.0 | |||
| Cervical vert. C4 length | 2.8 | 3.2 | 2.7 | ||
| Thoracic vert. T4 length | 3.2 | 3.9 | 2.7 | 4.0 | 1.51 |
| Lumbar vert. L4 length | 4.3 | 4.5 | 4.7 | 1.04 | |
| Caudal vert. C4 length | 5.5 | 5.0 | |||
| Scapula length | 20.0* | 21.7 | |||
| Humerus length | 21.0* | 21.5 | |||
| Ulna length | 14.6 | 17.5 | 1.20 | ||
| Ulna olecranon length | 4.6 | 5.7 | 1.24 | ||
| Ulna prox. articular breadth | 1.9 | 2.0 | 1.05 | ||
| Radius length | 11.0 | 10.0 | 11.7 | 1.17 | |
| Radius distal width | 2.7 | 3.0 | 2.5 | ||
| Radius distal thickness | 2.3 | 1.8 | 2.3 | ||
| Carpus length | 2.3 | 2.1 | 2.2 | 1.05 | |
| Pisiform length | 4.7 | 3.7 | |||
| Metacarpal length (Mc-III) | 7.8 | 6.1 | 6.5 | 1.07 | |
| Manual phalanx length (III-1) | 6.3 | 5.9 | 5.9 | 1.00 | |
| Manual phalanx length (III-2) | 3.3* | 2.6 | 3.8* | 1.48 | |
| Manual phalanx length (III-3) | 1.3* | 1.1 | 1.4 | 1.26 | |
| Ilium length (acetabular margin) | 12.4 | 12.4 | |||
| Acetabulum diameter | 2.8* | 3.1* | 3.1 | ||
| Femur length | 19.0 | 17.2 | |||
| Femur midshaft diameter (anteroposterior) | 2.2 | 2.3 | 2.0 | ||
| Femur midshaft diameter (bilateral) | 2.5 | 3.2 | 2.5 | ||
| Patella length | 3.1 | 4.1 | 2.9 | ||
| Patella width | 1.9 | 2.6 | 1.8* | ||
| Patella thickness | 1.9 | 2.3 | 1.6 | ||
| Tibia length | 21.0 | 18.6 | |||
| Astragalus length | 4.4 | 5.4 | 3.8 | ||
| Astragalus width | 2.1 | 2.3 | 2.0 | ||
| Astragalus height | 2.1 | 2.9 | 2.2 | ||
| Cuboid length | 1.9 | 2.7 | 1.9 | ||
| Metatarsus length (Mt-III) | 12.2 | 8.9 | |||
| Pedal phalanx length (III-1) | 9.0 | 7.0 | |||
| Pedal phalanx length (III-2) | 7.0 | 4.7 | |||
| Pedal phalanx length (III-3) | 2.3 | 1.8 | |||
| Median dimorphism | 1.12 | ||||
| 1Body weight (kg; estimate) | 400* | 410* | 280* | 390* | 1.39 * |
Sexes of the A. clavis and R. balochistanensis specimens are not known.
*
Asterisk indicates estimated measurement.
1
Body weight is estimated from the centrum size of available thoracic vertebrae, using multiple regression and a reference set of 13 marine mammal skeletons of known weight (8 cetaceans and 5 pinnipeds) spanning a range of 85 to 23,500 kg (see Figure 13). Weight for female Maiacetus inuus is estimated from male M. inuus in two ways: using the 12% average difference in comparable linear dimensions or the 4% average difference found for premolars and molars (Table 2).
2
Ratio based on measurements of male and female adult specimens in Maiacetus inuus.