Kinnareemimus (, meaning "Kinnaree mimic", after a figure from Thai folklore) is an extinct genus of ornithomimosaurian theropod dinosaur that was discovered in the Early Cretaceous Sao Khua Formation in what is now Thailand. The genus contains only the type species, K. khonkaenensis. The specific epithet is after Khon Kaen Province, which is in northeastern Thailand, where the remains of the animal were discovered.
Discovery and naming
Ornithomimosaur body fossils and ichnofossils were reported in Thailand's Khorat Plateau as early as 1997 in a publication by Eric Buffetaut and colleagues. At the time, only two dinosaur genera, Siamotyrannus and Phuwiangosaurus had been named from the country. Their report included a drawing of the metatarsals of an ornithomimosaur which had been uncovered at a locality called "Phu Wiang 5". These metatarsals clearly showed the derived arctometatasalian condition, similar to the ornithomimosaurs known from Laramidia. However, this specimen was not identified by any name other than the "Thai ornithomimosaur". The next mention of the "Thai ornithomimosaur" was in the first edition of the Dinosaur Press magazine, which was published in Japan in 2000. In this publication, the taxon is referred to by the nomen nudum "Ginnareemimus" by Ryuichi Kaneko, who wrote an article in the magazine which contained recent information about paleontology in Thailand. Kinnareemimus received a formal species description in 2009 when Eric Buffetaut, Varavudh Suteethorn, and Haiyan Tong published an anatomical monograph in the bulletin of the Geological Society of London. All the bones referable to ornithomimosaurs found at Phu Wiang 5 were disarticulated, and it is therefore impossible to know exactly how many individual animals were fossilized at the site. For this reason, when Kinnareemimus was described in 2009, only a single partial metatarsal III — designated PW5A-100 — was designated as the holotype. The remaining specimens were each given unique designations (from 101 to 131), and they were each referred to the new genus. Buffetaut and Suteethorn remark in their description that they are confident that all of the material belongs to a single species, but they conservatively did not include the anatomy of these bones in the species diagnosis. When it was described, the authors named the genus after Kinnaree, a being from the folklore of the Thai people which has the head and torso of a woman and the legs of a bird and lives in the legendary Himmapan Forest. Buffetaut and Suteethorn remark that the choice of Kinnaree was in reference to the birdlike feet of Kinnareemimus.
Description Because the holotype of Kinnareemimus is so fragmentary (consisting of only a single metatarsal), estimates of the animal's size have always been highly speculative and uncertain. The authors who described the genus, Eric Buffetaut and colleagues, did not give an estimate of the animal's mass. They remarked that the ratio of the lengths between the tibia and the third metatarsal of Kinnareemimus is most similar to Garudimimus. They interpret this to mean that its body proportions may have been more similar to that genus than to derived genera like Gallimimus or Struthiomimus. It has subsequently been estimated by Molina-Pérez and Larramendi to have been about 1.8 metres (5.9 ft) long and would have possibly weighed around 13 kilograms (29 lb).
Holotype
The holotype of Kinnareemimus (PW5A-100) is a partially complete third metatarsal that preserves the articular surface on the left side. The incompleteness of the specimen made it difficult for Buffetaut and colleagues to estimate the full size of the bone. However, another specimen (PW5A-101), is a second metatarsal of similar size and robustness, and is much more complete. The authors describing it believe it may have belonged to the same individual, and so they used it to estimate a full-length of the third metatarsal to have been roughly 145 millimetres (5.7 in) in life. This specimen was used to diagnose Kinnareemimus as distinct from all other ornithomimosaurs based on the following apomorphies: a semi-arctometatarsalian condition where the third metatarsal is still visible in proximal view and which narrows in the distal direction before flaring into a wider triangular cross-section at the distal-most end. This diagnosis was amended in 2024 by Samathi to include ventrally flattened pedal unguals with flexor fossae, which supported the inclusion of Kinnareemimus within ornithomimosauria.
Referred specimens Axial skeleton The only parts of the axial skeleton of Kinnareemimus which are preserved are eight vertebrae from various parts of the spine (one putative dorsal vertebra and seven caudal vertebra). The single non-caudal vertebra (PW5A-124) was inferred to be a dorsal vertebra because it lacks the articular facets for chevrons, although this is not known for certain. The neural arch for the vertebra is not preserved and the portion of the bone missing corresponds to the location of the unfused sutures in an immature individual, which led the authors to suggest the specimen came from a juvenile individual. The caudal vertebrae which are assigned to Kinnareemimus are from several distinct individuals. The centra are hourglass-shaped and hollow with no transverse processes, resembling the condition seen in Gallimimus. Some of the preserved vertebrae have differing cross-sectional shapes, and probably come from different sections of the tail. At least one (PW5A-130) may be a first caudal vertebra. The seven vertebrae preserved from other parts of the tail display varying degrees of fusion, indicating these specimens are from a multi-age assemblage.
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