page_title: Gallimimus
section_title: Palaeobiology
hierarchical_section_title: Gallimimus / Palaeobiology
caption_attribution_description: Gallimimus bullatus leg bones (specimen ZPAL MgD-I/8), Museum of Evolution of Polish Academy of Sciences, Warsaw.
context_page_description: Gallimimus is a genus of theropod dinosaur that lived in what is now Mongolia during the Late Cretaceous period, about seventy million years ago. Several fossils in various stages of growth were discovered by Polish-Mongolian expeditions in the Gobi Desert of Mongolia during the 1960s; a large skeleton discovered in this region was made the holotype specimen of the new genus and species Gallimimus bullatus in 1972. The generic name means "chicken mimic", referring to the similarities between its neck vertebrae and those of the Galliformes. The specific name is derived from bulla, a gold capsule worn by Roman youth, in reference to a bulbous structure at the base of the skull of Gallimimus. At the time it was named, the fossils of Gallimimus represented the most complete and best preserved ornithomimid material yet discovered, and the genus remains one of the best known members of the group.
  Gallimimus is the largest known ornithomimid; adults were about 6 metres long, 1.9 metres tall at the hip and weighed about 440 kilograms. As evidenced by its relative Ornithomimus, it would have had feathers. The head was small and light with large eyes that faced to the sides.
context_section_description: The cervical vertebrae of Gallimimus indicate that it held its neck obliquely, declining upwards at an angle of 35 degrees. Osmólska and colleagues found that the hands of Gallimimus were not prehensile (or capable of grasping), and that the thumb was not opposable. They also suggested that the arms were weak compared to, for example, those of the ornithomimosaur Deinocheirus. They agreed with the interpretations of ornithomimid biology by palaeontologist Dale Russell from earlier in 1972, including that they would have been very fleet (or cursorial) animals, although less agile than large, modern ground birds, and would have used their speed to escape predators. Russell also suggested that they had a good sense of vision and intelligence comparable to that of modern ratite birds. Since their predators may have had colour vision, he suggested it would have influenced their colouration, perhaps resulting in camouflage. In 1982, palaeontologist Richard A. Thulborn estimated that Gallimimus could have run at speeds of 42–56 km/h (29–34 mph). He found that ornithimimids would not have been as fast as ostriches, which can reach 70–80 km/h (43–49 mph), in part due to their arms and tails increasing their weight.
  In 1988, Paul suggested that the eyeballs of ornithomimids were flattened and had minimal mobility within the sockets, necessitating movement of the head to view objects. Since their eyes faced more sideways  than in some other bird-like theropods, their binocular vision would have been more limited, which is an adaptation in some animals that improves their ability to see predators behind them. Paul considered the relatively short tails, which reduced weight, and missing halluxes of ornithomimids to be adaptations for speed. He suggested that they could have defended themselves by pecking and kicking, but would have mainly relied on their speed for escape. In 2015, Akinobu Watanabe and colleagues found that together with Deinocheirus and Archaeornithomimus, Gallimimus had the most pneumatised skeleton among ornithomimosaurs. Pneumatisation is thought to be advantageous for flight in modern birds, but its function in non-avian dinosaurs is not known with certainty. It has been proposed that pneumatisation was used to reduce the mass of large bones, that it was related to high metabolism, balance during locomotion, or used for thermoregulation.
  In 2017, Lee and colleagues suggested various possible taphonomic circumstances (changes during decay and fossilisation) to explain how the Gallimimus foot discovered in 2009 was associated with a trackway. The trackway is preserved in sandstone while the foot is preserved in mudstone, extending 20 centimetres (7.9 in) below the layer with the tracks. It is possible the fossil represents an animal that died in its tracks, but the depth of the foot in the mud may be too shallow for it to have become mired. It may also have been killed by a flood, after which it was buried in a pond. However, the layers of mud and sand do not indicate flooding but probably a dry environment, and the disrupted sediments around the fossil indicate the animal was alive when it came to the area. The authors thus suggested that the tracks had been made over an extended amount of time and period of drying, and that probably none of them were produced by the individual that owned the foot. The animal may have walked across the floor of a pond, breaking through the sediment layer with the tracks while it was soaked from rain or contained water. The animal may have died in this position from thirst, hunger, or another reason, and mud then deposited on the sand, thereby covering and preserving the tracks and the carcass. The foot may have become clenched and disarticulated as it decomposed, which made the tendons flex, and was later stepped on by heavy dinosaurs. The area may have been a single bone bed (based on the possible number of poached specimens) representing a Gallimimus mass mortality, perhaps due to a drought or famine. The fact that the animals seem to have died at the same time (the empty excava
caption: Hindlimb bones of ZPAL MgD-I/8, MEPAS; note arctometatarsalian foot
exif: {"Image ImageWidth": "3264", "Image ImageLength": "1836", "Image Make": "samsung", "Image Model": "SM-G800F", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS3 Windows", "Image DateTime": "2018:05:22 18:59:29", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "240", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "12334", "Thumbnail JPEGInterchangeFormatLength": "5773", "EXIF ExposureTime": "1/17", "EXIF FNumber": "12/5", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "200", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2018:05:18 15:49:03", "EXIF DateTimeDigitized": "2018:05:18 15:49:03", "EXIF ShutterSpeedValue": "203/50", "EXIF ApertureValue": "63/25", "EXIF BrightnessValue": "27/100", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "63/25", "EXIF MeteringMode": "CenterWeightedAverage", "EXIF Flash": "Flash did not fire", "EXIF FocalLength": "33/10", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2244", "EXIF ExifImageLength": "1788", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF FocalLengthIn35mmFilm": "31", "EXIF SceneCaptureType": "Standard", "EXIF ImageUniqueID": ""}