page_title: Mosasaurus
section_title: Postcranial skeleton
hierarchical_section_title: Mosasaurus / Description / Postcranial skeleton
caption_attribution_description: English: Skull based on reconstruction from Street and Caldwell (2017). The number of vertebrae based on photos of almost complete skeleton of Mosasaurus missouriensis (TMP 2012.010.0001) which gives a rather conservative size estimate - around 14 meters along a curve with a scale up to CCMGE 10/2469 with 171 cm lower jaw. Cervical and dorsal vertebrae based on MNHN AC 9648, IRSNB R26 and NHMM 006696 from Lingham-Soliar (1995) and Street &amp; Caldwell (2017) papers as well as on the TMP 2012.010.0001. Tail completely based on TMP 2012.010.0001. Pectoral girdle, pelvic girdle, forelimb and hindlimb based on IRSNB R26, MNHN AC 9648, NHMM 1193024 and NHMM 006696. Rib cage scaled to fit TMP 2012.010.0001. Sternal elements speculative. A controversial part of reconstruction is the size of the limbs. I used data from Anne Schulp, not the scaling of limb bones of the IRSNB R12 from Lingham-Soliar (1995) because the latter specimen seems as young individual that may have disproportionately short limbs. The tail fluke is based on Lindgren et al. (2011) reconstruction, not on the ERMNH HFV 197, contrary to the recommendations of Lindgren in pers. due to sudden biomechanical problems with ERMNH HFV 197-like fluke in large mosasaurs. Русский: Череп основан на реконструкции от Street and Caldwell (2017). Количество позвонков основано на фотографиях почти полного скелета Mosasaurus missouriensis (TMP 2012.010.0001) и дает довольно консервативную оценку размера - около 14 метров по кривой с масштабом до CCMGE 10/2469 (171 см нижняя челюсть). Шейные и спинные позвонки реконструированы на основе зарисовок MNHN AC 9648, IRSNB R26 и NHMM 006696 из Lingham-Soliar (1995) и Street &amp; Caldwell (2017), а также фотографии TMP 2012.010.0001. Хвост полностью основан на TMP 2012.010.0001. Пояса конечностей и конечности основаны на зарисовках IRSNB R26, MNHN AC 9648, NHMM 1193024 и NHMM 006696. Грудная клетка масштабирована в соответствии с TMP 2012.010.0001. Элементы грудины спекулятивны. Спорной частью реконструкции является размеры конечностей. Я использовал данные от Anne Schulp, а не масштабирование костей конечностей IRSNB R12 на основе зарисовок из Lingham-Soliar (1995), потому что последний образец выглядит как молодая особь, у которой могут быть непропорционально короткие конечности. Хвостовой плавник основан на реконструкции из Lindgren et al. (2011), а не на ERMNH HFV 197, вопреки рекомендациям Линдгрена в персональной переписке из-за внезапных биомеханических проблем с хвостовыми плавниками по типа ERMNH HFV 197 у крупных мозазавров.
context_page_description: Mosasaurus is the type genus of the mosasaurs, an extinct group of aquatic squamate reptiles. The genus lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages of the Late Cretaceous. The earliest fossils known to science were found as skulls in a chalk quarry near the Dutch city of Maastricht in the late 1700s, which were initially thought to have been the bones of crocodiles or whales. One particular skull discovered at around 1780, and which was seized during the French Revolutionary Wars for its scientific value and transported to Paris, was famously nicknamed the "great animal of Maastricht". In 1808, naturalist Georges Cuvier concluded that it belonged to a giant marine lizard with similarities to monitor lizards but otherwise unlike any animal known today. This concept was revolutionary at the time and helped support the then-developing ideas of extinction. However, Cuvier did not designate a scientific name for the new animal; this task was completed by William Daniel Conybeare in 1822 when he named it Mosasaurus in reference to its origin in fossil deposits near the Meuse River.
context_section_description: The most complete skeleton of Mosasaurus, whose species-level identification is debated and is on display at the Museum of Geology at the South Dakota School of Mines and Technology under the catalog SDSM 452, has seven cervical vertebrae in the neck, thirty-eight dorsal vertebrae (which includes thoracic and lumbar vertebrae) in the back, and eight pygal vertebrae (front tail vertebrae lacking chevrons) followed by sixty-eight caudal vertebrae in the tail. All species of Mosasaurus have seven cervical vertebrae, but other vertebral counts vary among them. Various partial skeletons of M. conodon, M. hoffmannii (M. maximus), and M. missouriensis suggest that M. conodon likely had up to thirty-six dorsal vertebrae and nine pygal vertebrae; M. hoffmannii had likely up to thirty-two thoracic vertebrae and ten pygal vertebrae; and M. missouriensis around thirty-three dorsal vertebrae, eleven pygal vertebrae, and at least seventy-nine caudal vertebrae. M. lemmonieri had the most vertebrae in the genus, with up to around forty dorsal vertebrae, twenty-two pygal vertebrae, and ninety caudal vertebrae. Compared to other mosasaurs, the rib cages of Mosasaurus are unusually deep and form an almost perfect semicircle, giving it a barrel chest. Extensive cartilage likely connected the ribs with the sternum, which would have facilitated breathing movements and compression when in deeper waters. The texture of the bones is virtually identical with that in modern whales, which implies Mosasaurus enjoyed a high range of aquatic adaptability and neutral buoyancy seen in cetaceans.
  The tail is bilobed and hypocercal, which means that the tail vertebrae extends toward the lower lobe. The centra of the tail vertebrae gradually shorten around the center of the tail and lengthen behind the center, suggesting rigidness around the tail center and excellent flexibility posterior to it. Like most advanced mosasaurs, the tail bends slightly downwards as it approached the center, but this bend is at a small degree with little offset from the body. Mosasaurus also has large haemal arches in the caudal vertebrae that bend near the middle of the tail, which contrasts with the reduction of haemal arches in other marine reptiles such as ichthyosaurs. These and other features support a large and powerful paddle-like fluke in Mosasaurus.
  The forelimbs of Mosasaurus are wide and robust. The scapula and humerus are fan-shaped and wider than tall. The radius and ulna are short, but the former is taller and larger than the latter. The paddle is supported with five sets of finger-like metacarpals and phalanges with the fifth being shorter and offset from the rest. The overall structure of the paddle is compressed, similar to that in Plotosaurus, and is well-suited for utilization for faster swimming. In the hindlimbs, the paddle is supported with four sets of digits. The ilium is rod-like and slender; in M. missouriensis, it is around 1.5 times longer than the femur. The femur itself is about twice as long than it is wide and ends in a pair of distinct articular facets that meet at an angle of approximately 120°.
caption: Skeletal reconstruction of M. hoffmannii
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