Huehuecanautl (lat.: Huehuecanauhtlus) is a genus of dinosaurs from the superfamily Hadrosauroids (Hadrosauroidea), which lived in the territory of the modern Western Mexican state of Michoacan since the Santonian age of the Upper Cretaceous. It is represented by the only species Huehuecanauhtlus tiquichensis.
Huehuecanautl is known to science from the remains of only two individuals. The holotype no. IGM 6253 is represented by fragments of the skull (part of the left half of the maxillary bone and a fragment of the dentary) and a postcranial skeleton, including 4 cervical vertebrae, 9 dorsal vertebrae, 4 neural arches of the dorsal vertebrae, 1 superior articular process of the dorsal vertebrae, 5 right dorsal ribs, 7 left dorsal ribs, 7 neural arches of the sacral vertebrae, 7 superior articular processes of the sacral vertebrae, 1 superior articular process of the caudal vertebrae, 3 caudal vertebrae, 2 neural arches of the caudal vertebrae, 8 fragmentary ossified tendons, parts of the left and right halves of the ilium, and fragments left and right sides of the pubic bone.
Smaller paratype No. IGM 6254 includes a fragment of the left half of the dentary, 2 teeth and 1 anterior articular process of the cervical vertebra.
Both specimens were found in the area of Barranca los Bonetes (Spanish.: Barranca Los Bonetes) in the municipality of Tusantla, Michoacán.
The holotype of Huehuecanautl was found at fossil-bearing site 6, while the paratype was found at site 3 of an unnamed Upper Cretaceous Santonian Formation estimated to be about 85.8-83.5 million years old.
In 2012, a group of paleontologists led by Angel Alejandro Ramirez-Velasco (Spanish.: Angel Alejandro Ramírez-Velasco) identified this dinosaur as a separate genus by a unique combination of distinguishing features, in particular, by 2 teeth located in the occlusal plane of the rostral third of the dentary and the posterior third of the maxillary bone.
Huehuecanautl had 7 sacral vertebrae, while the posterior ones were equipped with high neural arches, which were 3.5-4 times higher than the centers of these vertebrae.
Like the Claosaurus (lat.: Claosaurus), the length of the supraacetabular process of the dinosaur is 75% of the length of the central part of the iliac wing, and its apex is located above the posteroventral angle of the tuberosity of the ischium.
Huehuecanautl differs from other hadrosauroids in having a very strongly inclined preacetabular process of the ilium, as a result of which the longitudinal axis of this process is located at an angle of less than 130 ° to the horizontal plane formed by the branches of the ischium and pubis.
It can be distinguished from basal hadrosauroids by the very deeply concave profile of the dorsomedial margin of the ilium adjacent to the supraacetabular process.
A phylogenetic analysis carried out in 2012 by the Ramirez-Velasco group revealed a wide polytomy (the presence of more than two secondary genealogical branches) in all hadrosauroids that are evolutionarily more highly developed compared to Probactrosaurus (lat.: Probactrosaurus), but less developed than hadrosaurids (Hadrosauridae).
An exception from this polytomy of such animals as the Claosaurus, Heyavati / Jeyavati (lat.: Jeyawati), Levnesovia (Levnesovia), Nanyangosaurus (Nanyangosaurus), Shuangmiaosaurus (Shuangmiaosaurus) and Telmatosaurus (Telmatosaurus), allowed to establish a more accurate topology.
The genus Huehuecanautl was first described and named in 2012 by paleontologists Angel Alejandro Ramirez-Velasco, Mulud Benammi (fr.: Mouloud Benammi), Albert Prieto-Marquez (Spanish.: Albert Prieto-Márquez), Jesús Alvarado Ortega and René Hernández-Rivera, with the type species named Huehuecanauhtlus tiquichensis.
The Latin generic name Huehuecanauhtlus is derived from the Nahua (from the name of the Aztec language Nahuatl) words huehuetl (“ancient”) and canauhtli (“duck”), indirectly indicating the presence in the dinosaur of the properties inherent in hadrosauroids.
Scientists appropriated him in honor of the Mexican city of Tikichyo (PSP.: Tiquicheo), as a sign of gratitude for the generosity and hospitality, provided by it by the inhabitants during paleontological research.