Bellatoripes

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Bellatoripes
Tyrannosaurid trackway.png
Bellatoripes fredlundi track and trackway in situ
Trace fossil classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: Tyrannosauridae
Ichnofamily: Tyrannosauripodidae
Ichnogenus: Bellatoripes
McCrea et al., 2014
Type ichnospecies
Bellatoripes fredlundi
McCrea et al., 2014

Bellatoripes (Latin for "warlike foot") is an ichnogenus of footprint produced by a large theropod dinosaur so far known only from the Late Cretaceous of Alberta and British Columbia in Canada. The tracks are large and three-toed, and based on their size are believed to have been made by tyrannosaurids, such as Albertosaurus and Daspletosaurus . Fossils of Bellatoripes are notable for preserving trackways of multiple individual tyrannosaurids all travelling in the same direction at similar speeds, suggesting the prints may have been made by a group, or pack, of tyrannosaurids moving together. Such inferences of behaviour cannot be made with fossil bones alone, so the record of Bellatoripes tracks together is important for understanding how large predatory theropods such as tyrannosaurids may have lived.

Contents

Discovery and classification

Excavation of the Bellatoripes track site in situ Bellatoripes digsite.png
Excavation of the Bellatoripes track site in situ

Bellatoripes was named in 2014 from a tracksite discovered in the Wapiti Formation, British Columbia containing the trackways of three separate track-makers, but isolated individual prints were already known prior to this discovery, including one from the Wapiti Formation and another from Dinosaur Provincial Park in Alberta. The trackway was first discovered by a local guide-outfitter Aaron Fredlund from two footprints in October 2011, and the rest of the track site was fully excavated by August 2012. Three distinct trackways were identified, Trackway A consisting of three footprints (the holotype specimen), Trackway B of just one, and Trackway C with two prints. The track types were assigned to a new ichnogenus and ichnospecies, Bellatoripes fredlundi, named after Fredlund for his discovery. [1]

The closest comparable ichnogenus to Bellatoripes in shape is Tyrannosauripus , a single track from the younger late Maastrichtian of New Mexico attributed to Tyrannosaurus . Bellatoripes is distinguished from Tyrannosauripus by its smaller size, lack of separate soft-tissue pad impressions along its digits, and hallux impressions that face forward (compared to the inward-facing hallux impression of Tyrannosauripus). Nonetheless, the close similarity in soft-tissue traits between the two ichnogenera prompted McCrea and colleagues to coin the ichnofamily Tyrannosauripodidae, to which they also referred similar, unnamed prints from the Nemegt Formation in Mongolia. The ichnofamily was named for the presumed track-makers of these prints, theropods from the family Tyrannosauridae. [1] [ failed verification ]

Bellatoripes and other tyrannosauripodids share a number of unique features that distinguish them from other known large theropod footprints, including a large heel pad and thick digits that lack distinct toe pads and taper in width towards the claws. Bellatoripes and other tyrannosauripodid tracks cannot be definitively assigned to Tyrannosauridae based on shared morphological traits alone, but the absence of other large theropods from the same geographical areas and stratigraphic ages precludes any other identities for the trackmakers. It is possible then that the soft-tissue features of Bellatoripes and tyrannosauripodid tracks are synapomorphies of Tyrannosauridae as a whole. [1]

Description

Photogrammetry of the Bellatoripes holotype trackway Bellatoripes photogrammetry.png
Photogrammetry of the Bellatoripes holotype trackway

Bellatoripes tracks are large, tridactyl, and bipedal pes prints, with the middle (third) toe being the longest (mesaxonic) and all toes bearing sharp, pointed claw impressions, typical of theropod footprints. The prints indicate the feet were robust and encased in thick soft tissues, including broad heel pads and thick digits that gradually taper out in thickness along their length. Bellatoripes footprints are over 50 centimetres (20 in) in length, and trackways record pace lengths of nearly 175 centimetres (5.74 ft) and strides of almost 350 centimetres (11.5 ft), leading to an estimated hip height for the track-maker at 2.3 metres (7.5 ft). A clawed hallux is preserved on some of the prints, but its identification has been disputed and these impressions have alternatively suggested to be from the base of the second toe. [1] [2]

Skin impressions of Bellatoripes preserve small, tuberculate scales, typical of theropod feet. [1]

Palaeobiology

The presence of three, parallel Bellatoripes trackways inferred to have been created in a short span of time is suggested to indicate that tyrannosaurids were social, gregarious animals that travelled in groups. Similar suggestions could only be made from skeletal evidence from body fossils alone, such as assemblages of multiple individuals preserved together at one locality. [3] The sedimentary conditions to preserve the tracks implies that they were made within a short span of time, and other tracks at the same site (including those of a hadrosaur and a smaller theropod) are more randomly oriented, implying that the animals were not constrained along the same path by a geographical barrier. Bellatoripes tracks are the first evidence from traces of living tyrannosaurids to support the suggestion that they lived in groups. [1]

The hypothesised movements of the Bellatoripes track-maker Bellatoripes trackmaking.png
The hypothesised movements of the Bellatoripes track-maker

The trackways of Bellatoripes allowed for the speed the track-maker was travelling at to be calculated, using the estimated hip height and stride lengths. This speed was calculated to be around 6.4 kilometres per hour (4.0 mph) to 8.5 kilometres per hour (5.3 mph), and is inferred to represent the preferred walking gait of tyrannosaurid theropods. Similarly, the age of the track-makers could be inferred from the dimensions of the footprints compared to the estimated hip height based upon contemporary tyrannosaurids that likely produced Bellatoripes tracks (Albertosaurus, Gorgosaurus , and Daspletosaurus). The track-makers were estimated to be between 25–29 years old, within the known upper age range of tyrannosaurid lifespans and indicating that the animals were mature adults. [1]

The fine preservation of the distal digits and small, parallel striations (interpreted as drag marks) within Bellatoripes tracks suggests that the track-makers partially withdrew their feet backwards before stepping forward, leaving the overlying sediment undisturbed. This contrasts with what is typically seen in other theropod footprints, where the tips of the digits drag as they are pulled forward, but is similar to the observed movements of ostrich feet during locomotion. [1] [4]

Palaeopathology

In the Wapiti Trackway A, the second digit of the left foot appears consistently truncated in both footprints #1 and #3, suggesting that the foot of the track-maker was injured in some way. The truncation suggests either the amputation of the claw and associated toe bone (phalanx) or a deformation or dislocation that kept the outer toe from contacting the ground, although the rough and uneven margin of the 'nub' at the tip of the impression suggests that the former is more likely from the loss of tissue and bone. Despite this, the dimensions of the trackway indicate that the injury did not negatively impact the animal's locomotion, with only a slight outward rotation of the right foot to compensate. The animal was otherwise moving at a similar speed and gait as those that produced the other trackways. [1]

Alternatively, Weems (2019) proposed that the truncation of digit II in trackway A was not an injury, but due to the trackmaker shifting its weight leftwards in response to its right foot sinking more deeply into the substrate, leaving an imperfect and poorly depressed digit II impression. [2]

Related Research Articles

<i>Albertosaurus</i> Genus of bipedal predatory dinosaur

Albertosaurus is a genus of large tyrannosaurid theropod dinosaur that lived in northwestern North America during the early to middle Maastrichtian age of the Late Cretaceous period, about 71 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which the genus is named, although an indeterminate species has been discovered in the Corral de Enmedio and Packard Formations of Mexico. Scientists disagree on the content of the genus and some recognize Gorgosaurus libratus as a second species.

<i>Tyrannosaurus</i> Genus of Late Cretaceous theropod

Tyrannosaurus is a genus of large theropod dinosaur. The type species Tyrannosaurus rex, often shortened to T. rex or colloquially T-Rex, is one of the best represented theropods. It lived throughout what is now western North America, on what was then an island continent known as Laramidia. Tyrannosaurus had a much wider range than other tyrannosaurids. Fossils are found in a variety of rock formations dating to the latest Campanian-Maastrichtian ages of the Late Cretaceous period, 72.7 to 66 million years ago. It was the last known member of the tyrannosaurids and among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction event.

<span class="mw-page-title-main">Tyrannosauridae</span> Family of dinosaurs

Tyrannosauridae is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to thirteen genera, including the eponymous Tyrannosaurus. The exact number of genera is controversial, with some experts recognizing as few as three. All of these animals lived near the end of the Cretaceous Period and their fossils have been found only in North America and Asia.

<i>Daspletosaurus</i> Genus of tyrannosaurid dinosaur from Late Cretaceous period

Daspletosaurus is a genus of tyrannosaurid dinosaur that lived in Laramidia between about 78 and 74.4 million years ago, during the Late Cretaceous Period. The genus Daspletosaurus contains three named species. Fossils of the earlier type species, D. torosus, have been found in Alberta, while fossils of a later species, D. horneri, have been found only in Montana. D. wilsoni has been suggested as an intermediate species between D. torosus and D. horneri that evolved through anagenesis, but this theory has been disputed by other researchers.

<i>Gorgosaurus</i> Genus of tyrannosaur dinosaur

Gorgosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.6 and 75.1 million years ago. Fossil remains have been found in the Canadian province of Alberta and the U.S. state of Montana. Paleontologists recognize only the type species, G. libratus, although other species have been erroneously referred to the genus.

<span class="mw-page-title-main">Tyrannosauroidea</span> Extinct superfamily of dinosaurs

Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period. By the end of the Cretaceous Period, tyrannosauroids were the dominant large predators in the Northern Hemisphere, culminating in the gigantic Tyrannosaurus. Fossils of tyrannosauroids have been recovered on what are now the continents of North America, Europe and Asia, with fragmentary remains possibly attributable to tyrannosaurs also known from South America and Australia.

<i>Grallator</i> Ichnogenus of dinosaur footprints

Grallator ["GRA-luh-tor"] is an ichnogenus which covers a common type of small, three-toed print made by a variety of bipedal theropod dinosaurs. Grallator-type footprints have been found in formations dating from the Early Triassic through to the early Cretaceous periods. They are found in the United States, Canada, Europe, Australia, Brazil and China, but are most abundant on the east coast of North America, especially the Triassic and Early Jurassic formations of the northern part of the Newark Supergroup. The name Grallator translates into "stilt walker", although the actual length and form of the trackmaking legs varied by species, usually unidentified. The related term "Grallae" is an ancient name for the presumed group of long-legged wading birds, such as storks and herons. These footprints were given this name by their discoverer, Edward Hitchcock, in 1858.

<i>Eubrontes</i>

Eubrontes is the name of fossilised dinosaur footprints dating from the Late Triassic and Early Jurassic. They have been identified from France, Poland, Slovakia, Czech Republic, Italy, Spain, Sweden, Australia (Queensland), US, India, China and Brazil (South).

<span class="mw-page-title-main">Albertosaurinae</span> Extinct subfamily of dinosaurs

Albertosaurines, or dinosaurs of the subfamily Albertosaurinae, lived in the Late Cretaceous of United States and Canada. The subfamily was first used by Philip J. Currie, Jørn H. Hurum, and Karol Sabath as a group of tyrannosaurid dinosaurs. It was originally defined as "(Albertosaurus + Gorgosaurus)", including only the two genera. The group is the sister clade to Tyrannosaurinae. In 2007, it was found that the group also contained Maleevosaurus, often synonymized with Tarbosaurus. However, this classification has not been accepted and Maleevosaurus is still considered a juvenile Tarbosaurus or Tyrannosaurus.

<span class="mw-page-title-main">Bird ichnology</span>

Bird ichnology is the study of avian life traces in ornithology and paleontology. Such life traces can include footprints, nests, feces and coproliths. Scientists gain insight about the behavior and diversity of birds by studying such evidence.

Megalosauripus is an ichnogenus that has been attributed to dinosaurs. The first ever appearance of this ichnospecies is 201 - 197 million years ago during the Early Jurassic period. The last recorded appearance was 156 - 151 million years ago during the Jurassic period.

<i>Prorotodactylus</i> Trace fossil

Prorotodactylus is a dinosauromorph or pterosauromorph ichnogenus known from fossilized footprints found in Poland and France. The prints may have been made by a dinosauromorph that was a precursor to the dinosaurs, possibly closely related to Lagerpeton. Fossils of Prorotodactylus date back to the early Olenekian stage of the Early Triassic, making it the oldest known dinosauromorph. Its presence during this time extends the range of the dinosaur stem lineage to the start of the Early Triassic, soon after the Permian-Triassic extinction event. Prorotodactylus is the only ichnogenus within the ichnofamily Prorotodactylidae. Two ichnospecies are known, the type P. mirus and P. lutevensis.

<i>Tyrannosauripus</i> Dinosaur footprint

Tyrannosauripus is an ichnogenus of dinosaur footprint. It was discovered by geologist Charles "Chuck" Pillmore in 1983 and formally described by Martin Lockley and Adrian Hunt in 1994. This fossil footprint from northern New Mexico is 96 cm long and given its Late Cretaceous age, it very likely belonged to the giant theropod dinosaur Tyrannosaurus rex. In 2016 the size of this individual was estimated at 11.4 meters and 5.8-6.9 tonnes. Similar tridactyl dinosaur tracks in North America were discovered earlier and named Tyrannosauropus in 1971, but they were later recognized as hadrosaurid tracks and their description deemed inadequate, with Tyrannosauropus regarded as a nomen dubium. True footprints likely from Tyrannosaurus would not be found until the discovery of Tyrannosauripus. In 2007, a large tyrannosaurid track was found also in eastern Montana. In 2016, a probable fossil trackway of Tyrannosaurus was discovered in Wyoming.

Abelichnus is an extinct ichnogenus of dinosaur footprint from the Candeleros Formation and the Rio Limay Formation. The type ichnospecies, Abelichnus astigerrae, was first discovered in Argentina in 1987 and was recorded as the biggest known dinosaur footprint ever discovered. Abelichnus probably grew to a size of 12.5-13 meters long.

Theropod paleopathology is the study of injury and disease in theropod dinosaurs. In 2001, Ralph E. Molnar published a survey of pathologies in theropod dinosaur bone that uncovered pathological features in 21 genera from 10 theropod families. Pathologies have been seen on most theropod body parts, with the most common sites of preserved injury and disease being the ribs and tail vertebrae. The least common sites of preserved pathology are the weight-bearing bones like the tibia, femur and sacrum. Most pathologies preserved in theropod fossils are the remains of injuries, but infections and congenital deformities have also been documented. Pathologies are less frequently documented in small theropods, although this may simply be because the larger bones of correspondingly larger animals would be more likely to fossilize in the first place.

<i>Nanuqsaurus</i> Extinct genus of dinosaurs

Nanuqsaurus is a genus of tyrannosaurine theropod dinosaur known from the Late Cretaceous period Prince Creek Formation of the North Slope of Alaska, having lived roughly 70-68 million years ago. It contains a single species, Nanuqsaurus hoglundi, known only from a partial skull and multiple undescribed postcranial and teeth elements.

<span class="mw-page-title-main">20th century in ichnology</span>

The 20th century in ichnology refers to advances made between the years 1900 and 1999 in the scientific study of trace fossils, the preserved record of the behavior and physiological processes of ancient life forms, especially fossil footprints. Significant fossil trackway discoveries began almost immediately after the start of the 20th century with the 1900 discovery at Ipolytarnoc, Hungary of a wide variety of bird and mammal footprints left behind during the early Miocene. Not long after, fossil Iguanodon footprints were discovered in Sussex, England, a discovery that probably served as the inspiration for Sir Arthur Conan Doyle's The Lost World.

Gwyneddichnium is an ichnogenus from the Late Triassic of North America and Europe. It represents a form of reptile footprints and trackways, likely produced by small tanystropheids such as Tanytrachelos. Gwyneddichnium includes a single species, Gwyneddichnium major. Two other proposed species, G. elongatum and G. minore, are indistinguishable from G. major apart from their smaller size and minor taphonomic discrepancies. As a result, they are considered junior synonyms of G. major.

Wakinyantanka is an ichnogenus of footprint produced by a large theropod dinosaur from the Late Cretaceous Hell Creek Formation of South Dakota. Wakinyantanka tracks are large with three long, slender toes with occasional impressions of a short hallux and narrow metatarsals. Wakinyantanka was the first dinosaur track to be discovered in the Hell Creek Formation, which remain rare in the preservational conditions of the rocks. The potential trackmakers may be a large oviraptorosaur or a small tyrannosaurid.

Farlowichnus is an ichnogenus of small theropod dinosaur footprint. It includes a single species, F. rapidus, known from prints found in the Early Cretaceous Botucatu Formation of Brazil. Farlowichnus is known from several fossil trackways that indicate that it was likely a cursorial animal that was well-adapted to desert environments.

References

  1. 1 2 3 4 5 6 7 8 9 McCrea, R. T.; Buckley, L. G.; Farlow, J. O.; Lockley, M. G.; Currie, P. J.; Matthews, N. A.; Pemberton, S. G. (2014). "A 'Terror of Tyrannosaurs': The First Trackways of Tyrannosaurids and Evidence of Gregariousness and Pathology in Tyrannosauridae". PLOS ONE . 9 (7): e103613. Bibcode:2014PLoSO...9j3613M. doi: 10.1371/journal.pone.0103613 . PMC   4108409 . PMID   25054328.
  2. 1 2 Robert E. Weems (2019). "Evidence for bipedal prosauropods as the likely Eubrontes track-makers". Ichnos: An International Journal for Plant and Animal Traces. 26 (3): 187–215. Bibcode:2019Ichno..26..187W. doi:10.1080/10420940.2018.1532902. S2CID   133770251.
  3. Currie, P.J; Eberth, D.A. (2010). "On gregarious behavior in Albertosaurus". Canadian Journal of Earth Sciences . 47 (9): 1277–1289. Bibcode:2010CaJES..47.1277C. doi:10.1139/e10-072.
  4. Avanzini, M.; Pinuela, L.; Garcia-Ramos, J. C. (2012). "Late Jurassic footprints reveal walking kinematics of theropod dinosaurs". Lethaia . 45 (2): 238–252. Bibcode:2012Letha..45..238A. doi:10.1111/j.1502-3931.2011.00276.x.