Terry Gates
I am a vertebrate paleontologist and evolutionary biologist creating citizen science initiatives to progress my research program and involve the public in the scientific process. My research focuses generally on the evolution of mega-herbivory and ornamental structures on dinosaurs. Additionally, I have an interest in the effect of geological events on the biogeographic distributions and subsequent ecological radiation of vertebrates. Ornithopod dinosaurs have been my primary model system over the past decade, although theropod and ceratopsian dinosaurs, along with galliform birds are now being incorporated.
Address: North Carolina Museum of Natural Sciences, Nature Research Center
121 W Jones St.
Raleigh, NC 27603
Address: North Carolina Museum of Natural Sciences, Nature Research Center
121 W Jones St.
Raleigh, NC 27603
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Papers by Terry Gates
Eolambia caroljonesa is the most abundant dinosaur in the lower Cenomanian Mussentuchit
Member of the Cedar Mountain Formation of Utah, and one of the most completely known
non-hadrosaurid iguanodontians from North America. In addition to the large holotype and
paratype partial skulls, copious remains of skeletally immature individuals, including three
bonebeds, have been referred to E. caroljonesa. Nevertheless, aspects of the postcranial
anatomy of this taxon, particularly the pelvic girdle, have remained ambiguous due to the
lack of associated postcranial material of larger, more mature individuals.
Methodology/Principal findings
Here we describe a recently discovered associated partial postcranial skeleton of a large
Eolambia caroljonesa. This specimen, FMNH PR 3847, provides new anatomical data
regarding the vertebral column and pelvic girdle, supplementing previous diagnoses and
descriptions of E. caroljonesa. A new phylogenetic analysis incorporating information from
FMNH PR 3847 places E. caroljonesa as a basal hadrosauromorph closely related to Protohadros
byrdi from the Cenomanian Woodbine Formation of Texas. Histological analysis of
FMNH PR 3847 reveals that it represents a subadult individual eight to nine years of age.
Taphonomic analysis indicates that FMNH PR 3847 was preserved in a crevasse splay
deposit, along with an unusual abundance of small crocodylomorph material.
that might otherwise remain unrecognized. Microfossil sampling is a particularly valuable tool for documenting
taxa that are poorly represented in macrofossil surveys due to small body size, fragile skeletal structure, or relatively low
ecosystem abundance. Because biodiversity patterns in the late Maastrichtian of North American are the primary data
for a broad array of studies regarding non-avian dinosaur extinction in the terminal Cretaceous, intensive sampling on
multiple scales is critical to understanding the nature of this event. We address theropod biodiversity in the Maastrichtian
by examining teeth collected from the Hell Creek Formation locality that yielded FMNH PR 2081 (the Tyrannosaurus
rex specimen “Sue”). Eight morphotypes (three previously undocumented) are identified in the sample, representing Tyrannosauridae,
Dromaeosauridae, Troodontidae, and Avialae. Noticeably absent are teeth attributed to the morphotypes
Richardoestesia and Paronychodon. Morphometric comparison to dromaeosaurid teeth from multiple Hell Creek and
Lance Formation microsites reveals two unique dromaeosaurid morphotypes bearing finer distal denticles than present
on teeth of similar size, and also differences in crown shape in at least one of these. These findings suggest more dromaeosaurid
taxa, and a higher Maastrichtian biodiversity, than previously appreciated.
sp. nov. is diagnosed on the basis of two unique traits, a hook-shaped projection of the nasal anteroventral process and
dorsal projection of the posteroventral process of the premaxilla, and is further differentiated from other hadrosaurid
species based on the morphology of the nasal (large nasal boss on the posterodorsal corner of the circumnarial fossa, small
protuberences on the anterior process, absence of nasal arch), jugal (vertical postorbital process), postorbital (high degree
of flexion present on posterior process), and squamosal (inclined anterolateral processes). This new taxon was discovered
in estuarine sediments dated at approximately 75 Ma and just 250 km north of the prolific dinosaur-bearing strata of the
Kaiparowits Formation, possibly overlapping in time with Gryposaurus monumentensis. Phylogenetic parsimony and
Bayesian analyses associate this new taxon with the Gryposaurus clade, even though the type specimen does not possess
the diagnostic nasal hump of the latter genus. Comparisons with phylogenetic analyses from other studies show that a
current consensus exists between the general structure of the hadrosaurid evolutionary tree, but on closer examination there
is little agreement among species relationships.
Basin (WIB) of North America have suggested the presence of faunal and floral provincialism, characterized
by distinct northern and southern ‘biomes.’ However, the “provincialism hypothesis” has been questioned
based largely on the contention that the investigated faunas were recovered from a series of diachronous,
time-transgressive deposits, and are therefore non-correlative.
Extensive work in several fossiliferous units of late Campanian age, including the Dinosaur Park, Judith River,
Two Medicine, Kaiparowits, Fruitland/Kirtland, and Aguja formations, has greatly increased understanding of
WIB vertebrate faunas and their chronostratigraphic relationships. Here updated and greatly expanded
faunal and chronostratigraphic datasets are utilized to undertake an extensive biogeographic analysis of
these six terrestrial fossiliferous formations within the WIB of North America. Quantitative biogeographic
comparisons of the formations and their constituent faunas are conducted using four statistical methods:
Analysis of Similarity, Q-mode cluster analysis, Parsimony Analysis of Endemicity, and Correspondence
Analysis.
The results of this study provide strong support for highly divergent faunas in northern and southern regions
of the WIB, with a latitudinal faunal gradient as an interface. Yet the nature of the interface between these
faunas remains unclear, with possibilities including: 1) two or more discrete provinces separated by a zone
(or zones) of faunal mixing; and 2) a continuous latitudinal gradient or cline, with no discrete zones of
endemism. Lacking evidence of any physiographic barrier to north–south dispersal, climatic variation within
the WIB is regarded as the most likely explanation for the overarching biogeographic patterns observed for
late Campanian vertebrate taxa.
Cerro del Pueblo Formation of Coahuila, Mexico, and the first lambeosaurine genus to be named from North America
in more than 70 years. Although the holotype specimen is a juvenile individual—as evidenced by its incomplete crest
development and relative size compared to other North American lambeosaurines—ontogeny independent autapomorphies
have been identified including quadrate with narrow quadratojugal notch and a postorbital with well developed,
dorsally positioned squamosal process. Additionally, this taxon is unique in that the prefrontal is not dorsally deflected
and anteroposteriorly expanded as in other lambeosaurine taxa of its size, but rather retains the frontal-prefrontal
“clamp” present in smaller individuals of other taxa. Phylogenetic analysis places Velafrons in a polytomy with numerous
other fan-crested lambeosaurines. The crest structure of Velafrons more closely resembles that of Corythosaurus and
Hypacrosaurus because it possesses an anteriorly projecting nasal process over the dorsal premaxilla process. Biogeographically,
Velafrons is one of three distinct hadrosaurids known from approximately 73.5 Ma—two lambeosaurines and
one hadrosaurine—all restricted to the southern region of the Western Interior Basin of North America.
Formation of southern Utah. Gryposaurus monumentensis, sp. nov. is distinguished from other Gryposaurus
species by possessing a more robust skull, enlarged clover-shaped prongs on the predentary oral margin, an
anteroposteriorly narrow infratemporal fenestra, and other autapomorphies plausibly associated with feeding
adaptations. The derived morphology revealed in G. monumentensis necessitates revision of the generic diagnosis
of Gryposaurus, including the addition of synapomorphies that further aid in distinguishing this taxon from
Kritosaurus. A revised phylogenetic analysis places Gryposaurus within a monophyletic clade that includes
Brachylophosaurus and Maiasaura. Gryposaurus monumentensis represents the most southern example of
Gryposaurus, and underlines the remarkable diversification and long duration of this genus. Based on the
phylogenetic, geographical, and stratigraphic evidence at hand, Gryposaurus was the most diverse genus within
Hadrosaurinae; it also possessed one of the largest geographical and stratigraphic distributions, spanning more
than five million years of the Campanian, and ranging from Alberta in the north to Utah (and possibly Texas) in
the south.
Eolambia caroljonesa is the most abundant dinosaur in the lower Cenomanian Mussentuchit
Member of the Cedar Mountain Formation of Utah, and one of the most completely known
non-hadrosaurid iguanodontians from North America. In addition to the large holotype and
paratype partial skulls, copious remains of skeletally immature individuals, including three
bonebeds, have been referred to E. caroljonesa. Nevertheless, aspects of the postcranial
anatomy of this taxon, particularly the pelvic girdle, have remained ambiguous due to the
lack of associated postcranial material of larger, more mature individuals.
Methodology/Principal findings
Here we describe a recently discovered associated partial postcranial skeleton of a large
Eolambia caroljonesa. This specimen, FMNH PR 3847, provides new anatomical data
regarding the vertebral column and pelvic girdle, supplementing previous diagnoses and
descriptions of E. caroljonesa. A new phylogenetic analysis incorporating information from
FMNH PR 3847 places E. caroljonesa as a basal hadrosauromorph closely related to Protohadros
byrdi from the Cenomanian Woodbine Formation of Texas. Histological analysis of
FMNH PR 3847 reveals that it represents a subadult individual eight to nine years of age.
Taphonomic analysis indicates that FMNH PR 3847 was preserved in a crevasse splay
deposit, along with an unusual abundance of small crocodylomorph material.
that might otherwise remain unrecognized. Microfossil sampling is a particularly valuable tool for documenting
taxa that are poorly represented in macrofossil surveys due to small body size, fragile skeletal structure, or relatively low
ecosystem abundance. Because biodiversity patterns in the late Maastrichtian of North American are the primary data
for a broad array of studies regarding non-avian dinosaur extinction in the terminal Cretaceous, intensive sampling on
multiple scales is critical to understanding the nature of this event. We address theropod biodiversity in the Maastrichtian
by examining teeth collected from the Hell Creek Formation locality that yielded FMNH PR 2081 (the Tyrannosaurus
rex specimen “Sue”). Eight morphotypes (three previously undocumented) are identified in the sample, representing Tyrannosauridae,
Dromaeosauridae, Troodontidae, and Avialae. Noticeably absent are teeth attributed to the morphotypes
Richardoestesia and Paronychodon. Morphometric comparison to dromaeosaurid teeth from multiple Hell Creek and
Lance Formation microsites reveals two unique dromaeosaurid morphotypes bearing finer distal denticles than present
on teeth of similar size, and also differences in crown shape in at least one of these. These findings suggest more dromaeosaurid
taxa, and a higher Maastrichtian biodiversity, than previously appreciated.
sp. nov. is diagnosed on the basis of two unique traits, a hook-shaped projection of the nasal anteroventral process and
dorsal projection of the posteroventral process of the premaxilla, and is further differentiated from other hadrosaurid
species based on the morphology of the nasal (large nasal boss on the posterodorsal corner of the circumnarial fossa, small
protuberences on the anterior process, absence of nasal arch), jugal (vertical postorbital process), postorbital (high degree
of flexion present on posterior process), and squamosal (inclined anterolateral processes). This new taxon was discovered
in estuarine sediments dated at approximately 75 Ma and just 250 km north of the prolific dinosaur-bearing strata of the
Kaiparowits Formation, possibly overlapping in time with Gryposaurus monumentensis. Phylogenetic parsimony and
Bayesian analyses associate this new taxon with the Gryposaurus clade, even though the type specimen does not possess
the diagnostic nasal hump of the latter genus. Comparisons with phylogenetic analyses from other studies show that a
current consensus exists between the general structure of the hadrosaurid evolutionary tree, but on closer examination there
is little agreement among species relationships.
Basin (WIB) of North America have suggested the presence of faunal and floral provincialism, characterized
by distinct northern and southern ‘biomes.’ However, the “provincialism hypothesis” has been questioned
based largely on the contention that the investigated faunas were recovered from a series of diachronous,
time-transgressive deposits, and are therefore non-correlative.
Extensive work in several fossiliferous units of late Campanian age, including the Dinosaur Park, Judith River,
Two Medicine, Kaiparowits, Fruitland/Kirtland, and Aguja formations, has greatly increased understanding of
WIB vertebrate faunas and their chronostratigraphic relationships. Here updated and greatly expanded
faunal and chronostratigraphic datasets are utilized to undertake an extensive biogeographic analysis of
these six terrestrial fossiliferous formations within the WIB of North America. Quantitative biogeographic
comparisons of the formations and their constituent faunas are conducted using four statistical methods:
Analysis of Similarity, Q-mode cluster analysis, Parsimony Analysis of Endemicity, and Correspondence
Analysis.
The results of this study provide strong support for highly divergent faunas in northern and southern regions
of the WIB, with a latitudinal faunal gradient as an interface. Yet the nature of the interface between these
faunas remains unclear, with possibilities including: 1) two or more discrete provinces separated by a zone
(or zones) of faunal mixing; and 2) a continuous latitudinal gradient or cline, with no discrete zones of
endemism. Lacking evidence of any physiographic barrier to north–south dispersal, climatic variation within
the WIB is regarded as the most likely explanation for the overarching biogeographic patterns observed for
late Campanian vertebrate taxa.
Cerro del Pueblo Formation of Coahuila, Mexico, and the first lambeosaurine genus to be named from North America
in more than 70 years. Although the holotype specimen is a juvenile individual—as evidenced by its incomplete crest
development and relative size compared to other North American lambeosaurines—ontogeny independent autapomorphies
have been identified including quadrate with narrow quadratojugal notch and a postorbital with well developed,
dorsally positioned squamosal process. Additionally, this taxon is unique in that the prefrontal is not dorsally deflected
and anteroposteriorly expanded as in other lambeosaurine taxa of its size, but rather retains the frontal-prefrontal
“clamp” present in smaller individuals of other taxa. Phylogenetic analysis places Velafrons in a polytomy with numerous
other fan-crested lambeosaurines. The crest structure of Velafrons more closely resembles that of Corythosaurus and
Hypacrosaurus because it possesses an anteriorly projecting nasal process over the dorsal premaxilla process. Biogeographically,
Velafrons is one of three distinct hadrosaurids known from approximately 73.5 Ma—two lambeosaurines and
one hadrosaurine—all restricted to the southern region of the Western Interior Basin of North America.
Formation of southern Utah. Gryposaurus monumentensis, sp. nov. is distinguished from other Gryposaurus
species by possessing a more robust skull, enlarged clover-shaped prongs on the predentary oral margin, an
anteroposteriorly narrow infratemporal fenestra, and other autapomorphies plausibly associated with feeding
adaptations. The derived morphology revealed in G. monumentensis necessitates revision of the generic diagnosis
of Gryposaurus, including the addition of synapomorphies that further aid in distinguishing this taxon from
Kritosaurus. A revised phylogenetic analysis places Gryposaurus within a monophyletic clade that includes
Brachylophosaurus and Maiasaura. Gryposaurus monumentensis represents the most southern example of
Gryposaurus, and underlines the remarkable diversification and long duration of this genus. Based on the
phylogenetic, geographical, and stratigraphic evidence at hand, Gryposaurus was the most diverse genus within
Hadrosaurinae; it also possessed one of the largest geographical and stratigraphic distributions, spanning more
than five million years of the Campanian, and ranging from Alberta in the north to Utah (and possibly Texas) in
the south.