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Monquirasaurus
Monquirasaurus ("Monquirá lizard") is an extinct genus of giant short-necked pliosaurs who lived during the Early Cretaceous (Aptian) in what is now Colombia. One species is known, M. boyacensis, described in 2021 from an almost complete fossil skeleton, discovered in 1977 in the town of Villa de Leyva, located in Boyacá. Published descriptions of the holotype specimen estimate that it should reach a total size approaching 9–11 m (30–36 ft) in length and weighing 9–14 metric tons (9.9–15.4 short tons), making Monquirasaurus a large representative of the pliosaurids.
The taxon has long been informally identified as a species belonging to the related genus Kronosaurus, even being named Kronosaurus boyacensis in a study published in 1992. This identification was due to the fact that the holotype specimen was banned from local access, and the descriptions were published with the help of photos. It was not until 2021 that a more complete description of the skeleton was made, confirming that it belonged to a separate genus.
The site where Monquirasaurus was discovered is the Paja Formation, that was once an environment containing a vast diversity of marine reptiles, including other large related pliosaurs, such as Stenorhynchosaurus and Sachicasaurus.
The holotype and only known specimen of Monquirasaurus is a 7.3 m (24 ft) long (as preserved), substantially incomplete (have many missing tail vertebrae) and articulated skeleton of a young adult animal discovered in 1977 by Samuel Vargas, Enrique Zubieta and German Zubieta on the lands of Tito Hurtado. Excavations were conducted by geologists, archaeologists and palaeontologists from the Instituto Colombiano de Geología y Minería (now Servicio Geológico Colombiano), the Instituto Colombiano de Antropología e Historia and the Universidad Nacional de Colombia.
Locally the specimen soon became known as "El Fósil", before being formally described as Kronosaurus boyacensis by Hampe in 1992 after being informally attributed to Kronosaurus in the years prior. This description however was conducted using photographs and remote imaging techniques, as the Junta de Acción Comunal and local community did not allow access to the holotype specimen, resulting in a lacking and untrustworthy description. It wasn't until 2021 that the specimen was reexamined first hand and described as a distinct genus, Monquirasaurus boyacensis. The holotype specimen still remains in the type locality, with the local "Museo El Fósil" having been built around the fossil.
The generic name derives from Monquirá, the Vereda (administrative division) where the holotype has been discovered. Similarly, the species name refers to the Boyacá Department.
Monquirasaurus was a relatively large pliosaur, with length estimates varying between 9.1 and 11.1 metres (30 and 36 ft) long and body mass estimates varying between 9 and 14 metric tons (9.9 and 15.4 short tons). In 2021, Noè & Gómez-Pérez suggested that a sexually mature, sub-adult individual would have measured 8 metres (26 ft) long.
The skull of Monquirasaurus is large and blunt, 2.45 m (8.0 ft) long from the snout tip to the posterior end of the right squamosal (2.65 to the posterior end of the retroarticular process of the mandible) and 1.2 m (3.9 ft) wide across the lateral margin of the quadrates. When viewed from the side the cranium is elongated and low, however it is still severely crushed. The jaws of the holotype are tightly closed and most of the dentition is preserved in situ. The cranium does not only suffer from crushing, but most of the dorsal surface is also heavily weathered and many bones are missing, making it almost impossible to observe most of the skull sutures. The skull has undulating margins, with three lateral expansions visible in dorsal view. The first is present along the lateral margins of the premaxilla, followed by an expansion around the large anterior caniniforms and one just beneath the orbits. A 4th expansion was probably also present in the posterior area of the skull, around the lateral margins of the temporal fenestra. Both anterior expansions are immediately followed by a medial constriction of the cranium. The nares are located 1.13 m (3.7 ft) from the snout tip, anterior to the orbits and on the same level as the 11th maxillary tooth. The mandible is preserved in better condition than the cranium, largely resisting the crushing that affected the latter. There is however still some dorsoventral compression present around the mandibular rami.
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Monquirasaurus
Monquirasaurus ("Monquirá lizard") is an extinct genus of giant short-necked pliosaurs who lived during the Early Cretaceous (Aptian) in what is now Colombia. One species is known, M. boyacensis, described in 2021 from an almost complete fossil skeleton, discovered in 1977 in the town of Villa de Leyva, located in Boyacá. Published descriptions of the holotype specimen estimate that it should reach a total size approaching 9–11 m (30–36 ft) in length and weighing 9–14 metric tons (9.9–15.4 short tons), making Monquirasaurus a large representative of the pliosaurids.
The taxon has long been informally identified as a species belonging to the related genus Kronosaurus, even being named Kronosaurus boyacensis in a study published in 1992. This identification was due to the fact that the holotype specimen was banned from local access, and the descriptions were published with the help of photos. It was not until 2021 that a more complete description of the skeleton was made, confirming that it belonged to a separate genus.
The site where Monquirasaurus was discovered is the Paja Formation, that was once an environment containing a vast diversity of marine reptiles, including other large related pliosaurs, such as Stenorhynchosaurus and Sachicasaurus.
The holotype and only known specimen of Monquirasaurus is a 7.3 m (24 ft) long (as preserved), substantially incomplete (have many missing tail vertebrae) and articulated skeleton of a young adult animal discovered in 1977 by Samuel Vargas, Enrique Zubieta and German Zubieta on the lands of Tito Hurtado. Excavations were conducted by geologists, archaeologists and palaeontologists from the Instituto Colombiano de Geología y Minería (now Servicio Geológico Colombiano), the Instituto Colombiano de Antropología e Historia and the Universidad Nacional de Colombia.
Locally the specimen soon became known as "El Fósil", before being formally described as Kronosaurus boyacensis by Hampe in 1992 after being informally attributed to Kronosaurus in the years prior. This description however was conducted using photographs and remote imaging techniques, as the Junta de Acción Comunal and local community did not allow access to the holotype specimen, resulting in a lacking and untrustworthy description. It wasn't until 2021 that the specimen was reexamined first hand and described as a distinct genus, Monquirasaurus boyacensis. The holotype specimen still remains in the type locality, with the local "Museo El Fósil" having been built around the fossil.
The generic name derives from Monquirá, the Vereda (administrative division) where the holotype has been discovered. Similarly, the species name refers to the Boyacá Department.
Monquirasaurus was a relatively large pliosaur, with length estimates varying between 9.1 and 11.1 metres (30 and 36 ft) long and body mass estimates varying between 9 and 14 metric tons (9.9 and 15.4 short tons). In 2021, Noè & Gómez-Pérez suggested that a sexually mature, sub-adult individual would have measured 8 metres (26 ft) long.
The skull of Monquirasaurus is large and blunt, 2.45 m (8.0 ft) long from the snout tip to the posterior end of the right squamosal (2.65 to the posterior end of the retroarticular process of the mandible) and 1.2 m (3.9 ft) wide across the lateral margin of the quadrates. When viewed from the side the cranium is elongated and low, however it is still severely crushed. The jaws of the holotype are tightly closed and most of the dentition is preserved in situ. The cranium does not only suffer from crushing, but most of the dorsal surface is also heavily weathered and many bones are missing, making it almost impossible to observe most of the skull sutures. The skull has undulating margins, with three lateral expansions visible in dorsal view. The first is present along the lateral margins of the premaxilla, followed by an expansion around the large anterior caniniforms and one just beneath the orbits. A 4th expansion was probably also present in the posterior area of the skull, around the lateral margins of the temporal fenestra. Both anterior expansions are immediately followed by a medial constriction of the cranium. The nares are located 1.13 m (3.7 ft) from the snout tip, anterior to the orbits and on the same level as the 11th maxillary tooth. The mandible is preserved in better condition than the cranium, largely resisting the crushing that affected the latter. There is however still some dorsoventral compression present around the mandibular rami.
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