Judithian
Encyclopedia
The Judithian was a North American faunal stage lasting from 83.5 to 70.6 million years ago. It overlaps with the Campanian
global stage.
even though they are the most abundant Judithian dinosaurs in the region. Large herbivores like the ceratopsians and hadrosaurs living in North America during the Late Cretaceous had "remarkably small georgraphic ranges" despite their large body size and high mobility. This restricted distribution strongly contrasts with modern mammalian faunas whose large herbivores' ranges "typical[ly] ... span much of a continent." Another example is Pentaceratops
, the only known Judithian ceratopsian from New Mexico
. In modern North America if one was to sample hypothetical future sites in southwestern Texas, northern New Mexico and southern Alberta, 34 of the 41 large mammal species in the continent could be represented, with the remainder's geographic ranges not overlapping with the sites. Roughly 20 species would be located at each site, but contrasting with the provinciality of dinosaurs, 11-16 species out of twenty would be shared between all three sites. Only the rarer species among modern mammal communities would be able to distinguish different latitudinal zones, and some of these taxa are likely too rare to fossilize. This lack of provinciality exists despite the strong temperature gradient. Restrictions in herbivorous dinosaur distribution may be due to foliage preferences, narrow tolerance for variation in climate or other environmental factors. The restrictions on herbivorous dinosaur distribution must have been due to ecological factors rather than physical barriers because carnivorous dinosaurs tended to have wider distributions, especially smaller forms.
As of his 2001 paper, restrictions in dinosaur occurrences based on distance from the paleo-shoreline had already been well documented. Vaguely distinguished inland-versus-coastal dinosaurs had been discussed previously in the scientific literature
. Terrestrial sedimentary strata from the Judithian to the Lancian
are generally regressive through-out the entire sequence the preserved changes in fossil communities represent not only phylogenetic changes but ecological zones from the submontane habitats to near-sea level coastal habitats. Modern life at high elevations in lower altitudes resembles life at low elevation in higher latitudes. There may be parallels to this phenomenon in Cretaceous ecosystems, for instance, Pachyrhinosaurus
is found in both Alaska and upland environments in southern Alberta. Northern and Southern animal biomes approximately correspond respectively with the Aquillapollenites
and Normapolles
palynofloral provinces.
takes the place of Centrosaurus
. Inland environments also differed, with the contemporary two medicine formation preserving an inland fauna characterized by Maiasaura
and the early pachyrhinosaur Einiosaurus
. Farther south was characterized by lower taxonomic diversity in communities where lambeosaurine were less common and centrosaurs were completely lacking. There Kritosaurus
, Parasaurolophus
and Pentaceratops
are the dominant fauna. The giant eusuchian Deinosuchus
is also "conspicuous" in the southern biome. Farther south, in Texas, Kritosaurus predominates. The biomes of the Eastern US may have resembled those of Texas except completely lacking in ceratopsians. Parasaurolophus and Kritosaurus are also present in northern latitudes, so evidently exchange between them occurred, but both are uncommon outside of the southern biome.
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
global stage.
Fauna
Dinosaur faunas of the Judithian age may represent the peak of dinosaur evolution in North America. Hadrosaurs were universally the dominant herbivore of the period and comprised more than half of "a typical assemblage." This was also the period of greatest generic diversity among large herbivorous dinosaurs. Just in Montana and Southern Alberta were ten genera of ceratopsians and ten genera of hadrosaurs.Paleobiogeography
Thomas M. Lehman has observed that Corythosaurus and Centrosaurus haven't been discovered outside of southern AlbertaAlberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
even though they are the most abundant Judithian dinosaurs in the region. Large herbivores like the ceratopsians and hadrosaurs living in North America during the Late Cretaceous had "remarkably small georgraphic ranges" despite their large body size and high mobility. This restricted distribution strongly contrasts with modern mammalian faunas whose large herbivores' ranges "typical[ly] ... span much of a continent." Another example is Pentaceratops
Pentaceratops
Pentaceratops is a genus of ceratopsid dinosaur from the late Cretaceous Period of what is now North America. The appearance of Pentaceratops sternbergii in the fossil record marks the end of the Judithian land vertebrate age and the start of the Kirtlandian...
, the only known Judithian ceratopsian from New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. In modern North America if one was to sample hypothetical future sites in southwestern Texas, northern New Mexico and southern Alberta, 34 of the 41 large mammal species in the continent could be represented, with the remainder's geographic ranges not overlapping with the sites. Roughly 20 species would be located at each site, but contrasting with the provinciality of dinosaurs, 11-16 species out of twenty would be shared between all three sites. Only the rarer species among modern mammal communities would be able to distinguish different latitudinal zones, and some of these taxa are likely too rare to fossilize. This lack of provinciality exists despite the strong temperature gradient. Restrictions in herbivorous dinosaur distribution may be due to foliage preferences, narrow tolerance for variation in climate or other environmental factors. The restrictions on herbivorous dinosaur distribution must have been due to ecological factors rather than physical barriers because carnivorous dinosaurs tended to have wider distributions, especially smaller forms.
As of his 2001 paper, restrictions in dinosaur occurrences based on distance from the paleo-shoreline had already been well documented. Vaguely distinguished inland-versus-coastal dinosaurs had been discussed previously in the scientific literature
Scientific literature
Scientific literature comprises scientific publications that report original empirical and theoretical work in the natural and social sciences, and within a scientific field is often abbreviated as the literature. Academic publishing is the process of placing the results of one's research into the...
. Terrestrial sedimentary strata from the Judithian to the Lancian
Lancian
-Geology:Terrestrial sedimentary strata from the Judithian to the Lancian are generally regressive through-out the entire sequence, so the preserved changes in fossil communities represent not only phylogenetic changes but ecological zones from the submontane habitats to near-sea level coastal...
are generally regressive through-out the entire sequence the preserved changes in fossil communities represent not only phylogenetic changes but ecological zones from the submontane habitats to near-sea level coastal habitats. Modern life at high elevations in lower altitudes resembles life at low elevation in higher latitudes. There may be parallels to this phenomenon in Cretaceous ecosystems, for instance, Pachyrhinosaurus
Pachyrhinosaurus
Pachyrhinosaurus is a genus of ceratopsid dinosaurs from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in Alberta, Canada, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species...
is found in both Alaska and upland environments in southern Alberta. Northern and Southern animal biomes approximately correspond respectively with the Aquillapollenites
Aquillapollenites
Aquillapollenites is an extinct morphogenus of Late Cretaceous pollen grain. North America's northern animal biome approximately correspond with the Aquillapollenites palynofloral province....
and Normapolles
Normapolles
Normapolles is an extinct morphogenus of Late Cretaceous pollen grain. North America's southern animal biome approximately correspond with the Normapolles palynofloral province....
palynofloral provinces.
Associations
An association between Centrosaurus and Corythosaurus is characteristic of southern Alberta. Earlier research had found that lambeosaurines are less common in contemporary Montanan strata and with different centrosaurs as MonocloniusMonoclonius
Monoclonius was a ceratopsian dinosaur from the Judith River Formation of Late Cretaceous Montana and Canada. It is often confused with Centrosaurus, a similar genus of ceratopsian . Monoclonius was described by Edward Drinker Cope in 1876...
takes the place of Centrosaurus
Centrosaurus
Centrosaurus is a genus of herbivorous ceratopsian dinosaurs from the late Cretaceous of Canada. Their remains have been found in the Dinosaur Park Formation and uppermost Oldman Formation, dating from 76.5 to 75.5 million years ago....
. Inland environments also differed, with the contemporary two medicine formation preserving an inland fauna characterized by Maiasaura
Maiasaura
Maiasaura is a large duck-billed dinosaur genus that lived in the area currently covered by the state of Montana in the Upper Cretaceous Period , about 74 million years ago....
and the early pachyrhinosaur Einiosaurus
Einiosaurus
Einiosaurus is a medium-sized centrosaurine ceratopsian from the Upper Cretaceous of northwestern Montana. The name means 'buffalo lizard', in a combination of Blackfeet Indian and Latinized Ancient Greek; the specific name Einiosaurus is a medium-sized centrosaurine (“short-frilled”)...
. Farther south was characterized by lower taxonomic diversity in communities where lambeosaurine were less common and centrosaurs were completely lacking. There Kritosaurus
Kritosaurus
Kritosaurus is an incompletely known but historically important genus of hadrosaurid dinosaur. It lived about 73 million years ago, in the Late Cretaceous of North America...
, Parasaurolophus
Parasaurolophus
Parasaurolophus is a genus of ornithopod dinosaur that lived in what is now North America during the Late Cretaceous Period, about 76.5–73 million years ago. It was an herbivore that walked both as a biped and a quadruped. Three species are recognized: P. walkeri , P. tubicen, and the...
and Pentaceratops
Pentaceratops
Pentaceratops is a genus of ceratopsid dinosaur from the late Cretaceous Period of what is now North America. The appearance of Pentaceratops sternbergii in the fossil record marks the end of the Judithian land vertebrate age and the start of the Kirtlandian...
are the dominant fauna. The giant eusuchian Deinosuchus
Deinosuchus
Deinosuchus is an extinct genus related to the alligator that lived 73 to 80 Ma , during the late Cretaceous period. The name translates as "terrible crocodile" and is derived from the Greek deinos , "terrible", and soukhos , "crocodile"...
is also "conspicuous" in the southern biome. Farther south, in Texas, Kritosaurus predominates. The biomes of the Eastern US may have resembled those of Texas except completely lacking in ceratopsians. Parasaurolophus and Kritosaurus are also present in northern latitudes, so evidently exchange between them occurred, but both are uncommon outside of the southern biome.
Reference
- Lehman, T. M., 2001, Late Cretaceous dinosaur provinciality: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 310–328.