Friday, June 5, 2015

[Paleontology • 2015] Regaliceratops peterhewsi • A New Horned Dinosaur Reveals Convergent Evolution in Cranial Ornamentation in Ceratopsidae

An artistic life reconstruction of the new horned dinosaur Regaliceratops peterhewsi in the palaeoenvironment of the Late Cretaceous of Alberta, Canada.
illustration: Julius T. Csotonyi. Courtesy of Royal Tyrrell Museum, Drumheller, Alberta. 

A photograph of the skull of the new horned dinosaur Regaliceratops peterhewsi (Royal Tyrrell Museum of Palaeontology 2005.055.0001) in oblique view.
Photo by Sue Sabrowski. | Courtesy of Royal Tyrrell Museum, Drumheller, Alberta. 

• A new horned dinosaur, Regaliceratops, is described based on a nearly complete skull
• It exhibits large nasal and small postorbital horns, and large frill epiossifications
• A derived chasmosaurine, the new animal shows centrosaurine-like display features
• Evidence for evolutionary convergence in horned dinosaur display is documented

Ceratopsid (horned) dinosaurs are an iconic group of large-bodied, quadrupedal, herbivorous dinosaurs that evolved in the Late Cretaceous and were largely restricted to western North America. Ceratopsids are easily recognized by their cranial ornamentation in the form of nasal and postorbital horns and frill (capped by epiossifications); these structures show high morphological disparity and also represent the largest cranial display structures known to have evolved. Despite their restricted occurrence in time and space, this group has one of the best fossil records within Dinosauria, showing a rapid diversification in horn and frill morphology. Here a new genus and species of chasmosaurine ceratopsid is described based on a nearly complete and three-dimensionally preserved cranium recovered from the uppermost St. Mary River Formation (Maastrichtian) of southwestern Alberta. Regaliceratops peterhewsi gen. et sp. nov. exhibits many unique characters of the frill and is characterized by a large nasal horncore, small postorbital horncores, and massive parietal epiossifications. Cranial morphology, particularly the epiossifications, suggests close affinity with the late Campanian/early Maastrichian taxon Anchiceratops, as well as with the late Maastrichtian taxon Triceratops. A median epiparietal necessitates a reassessment of epiossification homology and results in a more resolved phylogeny. Most surprisingly, Regaliceratops exhibits a suite of cranial ornamentations that are superficially similar to Campanian centrosaurines, indicating both exploration of novel display morphospace in Chasmosaurinae, especially Maastrichtian forms, and convergent evolution in horn morphology with the recently extinct Centrosaurinae. This marks the first time that evolutionary convergence in horn-like display structures has been demonstrated between dinosaur clades, similar to those seen in fossil and extant mammals.

Figure 2: Photographs and Interpretive Line Drawings of the Holotype of Regaliceratops peterhewsi gen. et sp. nov.
 (A–D) Nearly complete cranium, TMP 2005.055.0001, in right lateral (A), left lateral (B), rostral (C), and dorsal (D) views. (A′–D′) Interpretive drawings of photographed views in (A)–(D). 

Systematic Paleontology

Dinosauria Owen, 1842, sensu Padian and May, 1993.
Ornithischia Seeley, 1887, sensu Sereno, 1998.

Ceratopsia Marsh, 1888, sensu Dodson, 1997.

Ceratopsidae Marsh, 1888, sensu Sereno, 1998.
Chasmosaurinae Lambe, 1915, sensu Dodson et al., 2004.

Triceratopsini Longrich et al., 2011.

Regaliceratops gen. nov.

Type species: Regaliceratops peterhewsi gen. et sp. nov.

Diagnosis: as per the type and only species.

Regaliceratops peterhewsi gen. et sp. nov.

Etymology: Regaliceratops, from the Latin “regalis,” meaning “royal,” combined with the Greek “ceratops,” meaning “horned face.” The adjective “royal” refers to the crown-shaped parietosquamosal frill and epiossifications and the Royal Tyrrell Museum of Palaeontology (the “Royal” appellation was bestowed on the museum in 1990 by Her Majesty Queen Elizabeth II). The species epithet honors Peter Hews, who discovered the holotype.

Holotype: The holotype and only known specimen is Tyrrell Museum of Palaeontology (TMP) 2005.055.0001, a nearly complete cranium (skull excluding lower jaw) missing only the rostral bone. Palatal and braincase regions are obscured by matrix.

Figure 3: Time-Calibrated Phylogeny of Chasmosaurinae
 Time-calibrated strict consensus tree of five most parsimonious trees for Chasmosaurinae utilizing the new epiossification homology scheme (for tree details, see Figure S1B). For comparison of results and support indices, see Figure S1. Black bars indicate confident stratigraphic occurrence, whereas gray bars indicate less confidence. Stratigraphic information is derived from [17]. Bottom right: oblique view of the holotype of Regaliceratops peterhewsi, TMP 2005.055.0001.

Caleb M. Brown and Donald M. Henderson. 2015. A New Horned Dinosaur Reveals Convergent Evolution in Cranial Ornamentation in Ceratopsidae. Current Biology. DOI: 10.1016/j.cub.2015.04.041

New species of horned dinosaur with 'bizarre' features revealed via @physorg_com
This New Dinosaur Is Like Triceratops with a Massive Kickass Crown via @motherboard