Discoveries and species Pentaceratops

p. sternbergii holotype skull reconstructed parts, amnh

the first specimens collected charles hazelius sternberg in san juan basin in new mexico. sternberg worked in commission swedish uppsala university . in 1921 recovered skull , rump, specimens pmu r.200 , pmu r.286, @ meyers creek near kimbetoh wash, in layer of kirtland formation, sent fossils paleontologist carl wiman. in 1922 sternberg decided work on own account , north of tsaya trading post, in fossil forest of san juan county, discovered complete skeleton, sold american museum of natural history. museum sent out team headed charles mook , peter kaisen assist sternberg in securing specimen; subsequent digging sternberg in 1923 brought total of amnh specimens four. rump of main specimen discarded museum because had insufficient value display.

the species named , described henry fairfield osborn in 1923, pentaceratops sternbergii. generic name means five-horned face , derived greek penta (πέντα, meaning five), keras (κέρας, horn) , -ops (ὤψ, face), in reference 2 long epijugal bones, spikes protrude out sidewards under eyes, in addition 3 more obvious horns triceratops. osborn obligingly gave specific name sternbergii honoring discoverer veteran fossil hunter. name had been suggested osborn william diller matthew; specific epithet served consolation bankrupt sternberg 1923 fossils not acquired museum had use 1923/1924 budget process finds of great asian expeditions roy chapman andrews.

the holotype skull discovered sternberg in 1922, specimen amnh 6325. found in layer of fruitland formation, dating campanian, seventy-five million years old. other 3 amnh specimens amnh 1624, smaller skull; amnh 1622, pair of brow horns; , amnh 1625, piece of skull frill.

skull in new mexico museum of natural history , science

in 1930, wiman named second species of pentaceratops: pentaceratops fenestratus. based on sternberg s 1921 specimens , specific name referred hole in left squamosal. later considered same species pentaceratops sternbergii , junior synonym, hole being effect of injury.

in 1929 steinberg s son, george fryer sternberg, discovered specimen usnm v12002, right squamosal. pentaceratops proved quite common fossil in fruitland , kirtland formations. has been used guide fossil: appearance of pentaceratops sternbergii in fossil record marks end of judithian land vertebrate age , start of kirtlandian. subsequent finds include specimens mna pl. 1668, mna pl. 1747, nmmnh p-27468 , usnm 2416, partial skeletons skull; ypm 1229, skeleton lacking skull; ualp 13342 , ukvp 16100, skulls; unm b-1701, usnm 12741, usnm 12743, usnm 8604, smp vp-1596, smp vp-1488, smp vp-1500 , smp vp-1712, fragmentary skulls. apart san juan basin finds, juvenile specimen of pentaceratops, sdmnh 43470, has been reported williams fork formation of colorado in 2006.

specimen being airlifted new mexico national guard, 2015

sometimes identification of specimen pentaceratops has proven highly contentious. in 1998 thomas lehman described omnh 10165, large skull , associated skeleton found in new mexico in 1941, , presently on display @ sam noble oklahoma museum of natural history, being largest pentaceratops exemplar known, distinction of having produced largest known skull of land vertebrate. however, in 2011, skeleton renamed separate genus, titanoceratops, due more derived morphology closer triceratops , lack of unique characters shared pentaceratops proper.

in 2014 nicholas longrich named new species pentaceratops aquilonius, northern 1 , based on fragmentary fossils discovered during 1930s near manyberries in canada. species has been described having first epiparietal pointing upwards instead of forwards. in 2016, mallon et al. found p. aquilonius morphologically similar spiclypeus shipporum, possibly being same species, , considered p. aquilonius nomen dubium.