Baryonyx
The Baryonyx is a genus of theropod dinosaur of the family Spinosauridae
provided with a long narrow snout and a large claw on the thumb.
It includes for the moment that the case walkeri although some paleontologists
believe that the species Suchomimus tenerensis and Cristatusaurus
Lapparent are both species and Baryonyx Suchosaurus cultridens might be
be another.
This dinosaur lived in what is now England, Spain and Portugal in the Barremian
(Lower Cretaceous).
It is one of the few dinosaurs that we know precisely the diet and it is
currently the only non-avian theropod we are sure it was at least partly
piscivorous.
Etymology
He was appointed Baryonyx walkeri due to the impressive label he owned at the
first finger of each hand.
The genus name derives from Greek and βαρως / Barus meaning 'heavy', 'high' and
ονυξ / Onyx 'nail', 'Claw'.
The species name makes for his tribute to the discoverer of the animal, William
J. Walker
Description
Baryonyx walkeri is a dinosaur track to
70% and it lacks only a few bones of the skull, cervical and dorsal vertebrae,
ribs, bones of the feet and hands and most of the tail. It should be about 8
meters and a weight which was estimated at nearly 2 tons , making him a theropod
dinosaur sized. Baryonyx shares the characteristics of Spinosauridae which he
belongs. Indeed, it has a narrow snout and very stretched forward, powerful arms
bearing a large claw nail and sacral vertebrae higher than those of most other
theropods. The skull is typical of spinosauridés since the jaws are a large
number of conical teeth, slightly indented and cross section. In addition, the
anterior part of snout and lower jaw has a spatula (or spoon) resulting from an
enlargement of the lateral premaxilla, maxillae and dental. A depression called
'subrostrale is also present and gives the jaws a sigmoid shape in lateral view
. This theropod is different, however other members of spinosauridés a slight
tear subrectangulaire horn and other differences in the morphology of the sacral
and caudal vertebrae, pelvis and fibula.
Systematics
The systematic Baryonyx was heavily
debated in the 90s, Charig and Milner believed that this new genre was
part of the new family Baryonychidae and Buffetaut seeing him more in the
family Spinosauridae just like Spinosaurus. A consensus now seems to exist and
this theropod is now classified in the subfamily Baryonychinae with Suchomimus
tenerensis, Cristatusaurus Lapparent and Suchosaurus cultridens . The
Baryonychinae are thus the sister group of Spinosaurinae within the family
Spinosauridae. They differ from spinosaurinés (which include types Irritator
challengeri, Angaturama limai and Spinosaurus aegyptiacus) with finely
crenulated teeth and nasal cavity in front of the nose . Some paleontologists
consider the kind Suchomimus as a junior synonym of Baryonyx and should thus be
renamed Baryonyx tenerensis. Indeed, few osteological characters differentiating
these two dinosaurs (see article on Spinosauridae) and those paleontologists
believe that the few differences between Suchomimus Baryonyx and in no way
justify the designation of two different genera.
Discovery
Baryonyx walkeri was found in the pit of clay Smokejacks (owned
by the brick factory 'Ockley Brick Company') Wallis Wood near Ockley a town near
Dorking in Surrey, England. It was discovered during the winter of 1983 by
William J. Walker who first found that the enormous nail claw of the animal
which lacked only the front part. Assisted by several of his friends, he
nevertheless found the tip of the huge claws and other bones a week later.
Recognizing the importance of his discovery, the amateur paleontologist
contacted paleontologists Alan J. Charig and Angela C. Milner, both
paleontologists at the Natural History Museum, began excavations in the spring
of 1983. The team of paleontologists who was taken by these scientists
disengaged not less than two tons of rocks (clays called 'Wealden') containing
the bones of the animal .
The Baryonyx walkeri of Spain was also discovered during an excavation campaign
in 1983 in the town of Igea. The jaw fragment was then stored in the collections
of the 'Sección de Geología de la Sociedad de Ciencias Aranzadi' and described
in 1995 .
The first remains associated with the kind Baryonyx sp. (but interpreted as such
later) were discovered well before the end of the twentieth century as teeth
identical or very close to those of Baryonyx walkeri was discovered in Surrey
early nineteenth century . Indeed, Gideon Mantell, the famous paleontologist who
named the first dinosaur (Megalosaurus), was mentioned in 1827 such teeth from
the Wealden of Tilgate Forest (Surrey), but combined with a Crocodile . In 1841,
Sir Richard Owen, the founding father of the term 'Dinosauria', published in its
description Odontography teeth mentioned by Mantell and also closer to a
crocodile that called Suchosaurus . The type specimen upon which the species
Suchosaurus girardi which was created by Owen includes only a single
isolated tooth that seems close but not identical to that of Baryonyx . This is
therefore a baryonychiné which could be a different kind of Baryonyx. In 1897,
Savage described the remains from Portugal he identified as belonging to the new
species Suchosaurus cultridens . This species was recognized as a Baryonyx .
Currently, the last remains discovered (and published) by Baryonyx teeth are
isolated from the Province of Burgos and described in 2003
Palaeogeography
The species Baryonyx walkeri was found in Surrey but also
in Spain since a jaw fragment from the Province of La Rioja was identified as
belonging to this species . Other bones were associated with gender Baryonyx sp.
and come from other parts of Europe. Teeth and a vertebra sacred Baryonyx were
extracted from the cliffs of the Isle of Wight in England that are particularly
rich in vertebrate fossils from the Cretaceous lower . Isolated teeth of
Baryonyx were also discovered in the province of Burgos, Spain . Finally, most
recently, the material here Suchosaurus girardi discovered in the Province
of Lisboa and Setubal in Portugal and includes a piece of dental law and some
isolated teeth, was re-identified as that of spinosauridé Baryonyx . So
Baryonyx was present throughout Western Europe in the Lower Cretaceous. Some
scientists estimate that Baryonyx had also colonized parts of northern
Africa (Niger) to the Aptian and Albian.
Paleobiology
The discovery of Baryonyx walkeri is outstanding is because
paleontologists have found in the stomach region of the animal teeth and scales
of fish called lepidota who were attacked by stomach acids, as well as
disarticulated skeletal remains of a young Iguanodon . This discovery thus
provides a very valuable testimony of the last meal Baryonyx who ate well (at
least partially) of fish and herbivorous dinosaurs.
The theory that eating can be Spinosauridae was proposed by Taquet in
1984, even before being published the discovery of Baryonyx. Spinosauridés These
appear to be in effect in this specialized diet when you look in detail the
anatomy of the skeleton. The skull resembles greatly that of our current
crocodiles as it is stretched forward and with a narrow snout laterally. This
feature anatomically reduces the friction forces in the water and increase the
speed of any movement forward, such as that being done gavials the current to
catch fish. It has also been shown recently that the functional anatomy of
Baryonyx is closer to that of a Crocodile, by a crocodile or a theropod
Allosaurus as . Note also that a narrow skull is particularly vulnerable
compared to a massive head like a Tyrannosaurus or Carcharodontosaurus and it is
certain that spinosauridés should in no case be super-predators. Depression
subrostrale also allows the maxillary anterior teeth pointing forward which
facilitates any of prey taken during a forward movement [11]. In addition, the
teeth are conical, as are those of crocodilians, and particularly long. The
teeth of circular section generally reflect a diet of fish-eating because they
can punch the prey rather than shredding them. The absence of serrated teeth on
the show as it is used in any cutting, as is the case of the teeth of carnivores
whose only function is to cut the meat. The nostrils are retracted backwards and
the nasal opening should perhaps be at the top of the skull which would perhaps
allow spinosauridés plunging part of the snout in the water while continuing to
breathe. Other anatomical features present in skeletal portcrânien also go in
the direction of a piscivorous diet. The neck 'S' typical theropod is
particularly long this would give the animal can stand, body parallel to the
ground and plunged his head into the water in search of prey. Finally, the claw
of the thumb is too large and seems ready made to enable spinosauridés to
harpoon prey . The remains of a herbivorous dinosaur, however, show that
Baryonyx should not be exclusively ichthyophagous. Further evidence of feeding
spinosauridés have also shown that they also ate pterosaurs . It is more than
probable that these theropods were also eat carcasses and should have more ease
than other carnivorous dinosaurs to capture flying reptiles in flight . Some
paleontologists are also Baryonyx as a large predator or a scavenger super
rather than fish-eating animals, although this is refuted by other
paleontologists .
