Smok (archosaur)
Encyclopedia
Smok is an extinct genus
of large carnivorous archosaur
. It lived during the latest Triassic
period (latest Norian
to early Rhaetian
stage, about 205–200 Ma) in what is now Lisowice
, southern Poland
. The type species
is Smok wawelski (after the Wawel Dragon) and was named in 2011
. It is larger than any other known predatory archosaur
from the Late Triassic or Early Jurassic of central Europe. The relation of Smok to other archosaurs has not yet been thoroughly studied; it may be a rauisuchia
n or ornithosuchid crurotarsan (part of the crocodile line of archosaurs) or a theropod dinosaur (part of the bird line of archosaurs).
Several features indicate that Smok is an archosaur
, including serrated teeth, a contact between the jugal
and quadratojugal
bones at the back of the skull, a hole in front of the eye socket called the antorbital fenestra
, maxilla
e bones in the upper jaw that connect along their palatal
processes, and a rounded projection on the upper part of the femur
bone.
The braincase of Smok includes many derived
(advanced) features. The most prominent of these is a funnel-shaped structure on the bottom of the braincase, formed by a very wide, rounded basisphenoid bone. A deep notch called the basisphenoid recess cuts into the back of this funnel. Above the funnel is a very thin area of the braincase that is formed by deep depressions on the basisphenoids.
Smok has several features that are shared with both dinosaurs and crocodile-line archosaurs, making classification difficult. Similarities with theropods include a groove, or antitrochanter, on the ilium
bone of the hip that is part of the acetabulum
(a depression where the head of the femur attaches to the hip). Smok and theropods also have an anterior trochanter
on the femur. Some large theropods share with Smok the deep depressions of the basisphenoids in the braincase. Similarities with rauisuchians include a triangular antorbital fenestra and a connection between the ectopterygoid and jugal bones of the skull that is split into two projections. The hip of Smok has a ridge on the lateral surface of the ilium above the acetabulum. This ridge is a defining characteristic of rauisuchians, forming a buttress over the femur and giving these animals a pillar-erect stance.
Other features of Smok seem to exclude it from these groups of archosaurs. The premaxilla
and maxilla
of the upper jaw attach closely to each other, making a continuous row of evenly spaced teeth. Early theropods and orthithosuchids have a toothless gap between the premaxilla and the maxilla, distinguishing them from Smok. The upper jaw bones of rauisuchians are not closely connected, leaving a small opening between the premaxilla and maxilla that is not seen in Smok. Unlike many rauisuchians and theropods, Smok does not have pneumatic areas, or air pockets, in the braincase. It also has several features that link it with primitive archosauromorphs, including the presence of a postfrontal bone on the skull and a closed acetabulum in the hip.
to early Rhaetian
in age. This area was known to contain Triassic fossils since it was formally described in 2008. The first material of Smok, the jawbone and fragments of the skull, was discovered in 2007. It was first described in 2008 as a theropod dinosaur based on features in its braincase and frontal bone
. The material was also thought to represent two individuals. Similarities were noted between the braincase of the animal and that of allosaurs. When the discovery was first announced, it was called "the Dragon of Lisowice" and was purported to be the first member of a line of dinosaurs that led to Tyrannosaurus rex. Bones from other parts of the body were found in 2009 and 2010. Five tracks made by a three-toed archosaur – presumably a theropod dinosaur – were found in rocks that were 1 metres (3.3 ft) above the layer where Smok was found. The footprints may belong to Smok, but the lack of foot bones in the skeleton make this association uncertain.
Smok is known from the holotype
ZPAL V.33/15, a partially complete braincase which is associated with a partially preserved skeleton
, including cranial and postcrania
l bones from the referred materials ZPAL V.33/16-56, 97-102, 295-314, 434 and 507. All specimens were found in the same location (Lipie Śląskie clay-pit Formation) and probably represent a single individual. It was first named by Grzegorz Niedźwiedzki, Tomasz Sulej and Jerzy Dzik in 2011. Smok was named after the mythological Polish dragon of the same name that lived in a cave near the excavation site. The cave was on Wawel Hill
, the namesake of the type species S. wawelski.
and the rauisuchians Polonosuchus
and Teratosaurus
, but these animals were much smaller than Smok. It was one of the largest archosaurs in the world during the Late Triassic, and larger archosaurs did not appear until after the Early Jurassic. Smok lived alongside small carnivorous dinosauromorph and poposauroid archosaurs and large herbivorous dicynodonts.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of large carnivorous archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...
. It lived during the latest Triassic
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...
period (latest Norian
Norian
The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...
to early Rhaetian
Rhaetian
The Rhaetian is in geochronology the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It lasted from 203.6 ± 1.5 to 199.6 ± 0.6 million years ago...
stage, about 205–200 Ma) in what is now Lisowice
Lisowice, Silesian Voivodeship
Lisowice is a village in the administrative district of Gmina Pawonków, within Lubliniec County, Silesian Voivodeship, in southern Poland. It lies approximately south-east of Pawonków, west of Lubliniec, and north-west of the regional capital Katowice....
, southern Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is Smok wawelski (after the Wawel Dragon) and was named in 2011
2011 in paleontology
-Lobopods:-Arachnids:-Insects:-Newly named jawless vertebrates:-Newly named acanthodian:-Newly named cartilaginous fishes:-Newly named bony fishes:-Newly named lepospondyls:-Newly named temnospondyls:-Newly named lissamphibians:...
. It is larger than any other known predatory archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...
from the Late Triassic or Early Jurassic of central Europe. The relation of Smok to other archosaurs has not yet been thoroughly studied; it may be a rauisuchia
Rauisuchia
Rauisuchia is a group of predatory and mostly large Triassic archosaurs. As a clade, Rauisuchia includes these Triassic forms and all crocodylomorphs, which are descendants of Triassic rauisuchians. The group in its traditional sense is paraphyletic, because it does not include crocodylomorph...
n or ornithosuchid crurotarsan (part of the crocodile line of archosaurs) or a theropod dinosaur (part of the bird line of archosaurs).
Description
At an estimated 5 to 6 m (16.4 to 19.7 ft) in length, Smok was the largest carnivorous archosaur in central Europe at the time. It was larger than any other known theropod dinosaur or rauisuchian crurotarsan living in central Europe during either the Late Triassic or Early Jurassic. The skull is 50 to 60 cm (19.7 to 23.6 in) long.Several features indicate that Smok is an archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...
, including serrated teeth, a contact between the jugal
Jugal
The jugal is a skull bone found in most reptiles, amphibians, and birds. In mammals, the jugal is often called the malar or Zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species....
and quadratojugal
Quadratojugal
The quadratojugal is a small jaw bone that is present in most amphibians, reptiles, and birds, but has been lost in mammals. It is connected to the jugal as well as other bones, though these may vary with species....
bones at the back of the skull, a hole in front of the eye socket called the antorbital fenestra
Antorbital fenestra
An antorbital fenestra is an opening in the skull, in front of the eye sockets. This skull formation first appeared in archosaurs during the Triassic Period. Living birds today possess antorbital fenestrae, but the feature has been lost in modern crocodilians...
, maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
e bones in the upper jaw that connect along their palatal
Palate
The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...
processes, and a rounded projection on the upper part of the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
bone.
The braincase of Smok includes many derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
(advanced) features. The most prominent of these is a funnel-shaped structure on the bottom of the braincase, formed by a very wide, rounded basisphenoid bone. A deep notch called the basisphenoid recess cuts into the back of this funnel. Above the funnel is a very thin area of the braincase that is formed by deep depressions on the basisphenoids.
Smok has several features that are shared with both dinosaurs and crocodile-line archosaurs, making classification difficult. Similarities with theropods include a groove, or antitrochanter, on the ilium
Ilium
-Places:* Ilion or, Latinized, Ilium, another name for the legendary city of Troy, hence the title of Homer's Iliad*Ilium , an ancient city in Epirus...
bone of the hip that is part of the acetabulum
Acetabulum
The acetabulum is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.-Structure:...
(a depression where the head of the femur attaches to the hip). Smok and theropods also have an anterior trochanter
Trochanter
In human anatomy, the trochanter is a part of the thigh bone. It can refer to:* Greater trochanter* Lesser trochanter* Third trochanter-See also:* Intertrochanteric crest* Intertrochanteric line...
on the femur. Some large theropods share with Smok the deep depressions of the basisphenoids in the braincase. Similarities with rauisuchians include a triangular antorbital fenestra and a connection between the ectopterygoid and jugal bones of the skull that is split into two projections. The hip of Smok has a ridge on the lateral surface of the ilium above the acetabulum. This ridge is a defining characteristic of rauisuchians, forming a buttress over the femur and giving these animals a pillar-erect stance.
Other features of Smok seem to exclude it from these groups of archosaurs. The premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
and maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
of the upper jaw attach closely to each other, making a continuous row of evenly spaced teeth. Early theropods and orthithosuchids have a toothless gap between the premaxilla and the maxilla, distinguishing them from Smok. The upper jaw bones of rauisuchians are not closely connected, leaving a small opening between the premaxilla and maxilla that is not seen in Smok. Unlike many rauisuchians and theropods, Smok does not have pneumatic areas, or air pockets, in the braincase. It also has several features that link it with primitive archosauromorphs, including the presence of a postfrontal bone on the skull and a closed acetabulum in the hip.
History
Smok was found in a locality near Lisowice village that is latest NorianNorian
The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...
to early Rhaetian
Rhaetian
The Rhaetian is in geochronology the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It lasted from 203.6 ± 1.5 to 199.6 ± 0.6 million years ago...
in age. This area was known to contain Triassic fossils since it was formally described in 2008. The first material of Smok, the jawbone and fragments of the skull, was discovered in 2007. It was first described in 2008 as a theropod dinosaur based on features in its braincase and frontal bone
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
. The material was also thought to represent two individuals. Similarities were noted between the braincase of the animal and that of allosaurs. When the discovery was first announced, it was called "the Dragon of Lisowice" and was purported to be the first member of a line of dinosaurs that led to Tyrannosaurus rex. Bones from other parts of the body were found in 2009 and 2010. Five tracks made by a three-toed archosaur – presumably a theropod dinosaur – were found in rocks that were 1 metres (3.3 ft) above the layer where Smok was found. The footprints may belong to Smok, but the lack of foot bones in the skeleton make this association uncertain.
Smok is known from the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
ZPAL V.33/15, a partially complete braincase which is associated with a partially preserved skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
, including cranial and postcrania
Postcrania
Postcrania[p] in zoology and vertebrate paleontology refers to all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g...
l bones from the referred materials ZPAL V.33/16-56, 97-102, 295-314, 434 and 507. All specimens were found in the same location (Lipie Śląskie clay-pit Formation) and probably represent a single individual. It was first named by Grzegorz Niedźwiedzki, Tomasz Sulej and Jerzy Dzik in 2011. Smok was named after the mythological Polish dragon of the same name that lived in a cave near the excavation site. The cave was on Wawel Hill
Wawel Hill
Wawel Hill is the name of a Jurassic limestone outcrop formed about 150 million years ago. It is situated on the left bank of the Vistula River in Kraków, Poland, at an altitude of 228 metres above the sea level. Over the millennia, the hill provided a safe haven for people who settled there since...
, the namesake of the type species S. wawelski.
Paleobiology
Smok was the largest predator in its environment. Other large predatory archosaurs included the dinosaur LiliensternusLiliensternus
Liliensternus was a genus of coelophysoid dinosaur from the Late Triassic period, about 205 Ma.Liliensternus was originally named in 1934 by Friedrich von Huene as a second species of Halticosaurus, H. liliensterni, the specific name honouring the German amateur paleontologist, Dr...
and the rauisuchians Polonosuchus
Polonosuchus
Polonosuchus is a genus of rauisuchian known from the late Triassic of Poland.It was described as Teratosaurus silesiacus in 2005 by Tomasz Sulej, and was transferred to the genus Polonosuchus by Brusatte et al. in 2009....
and Teratosaurus
Teratosaurus
Teratosaurus was a genus of rauisuchian known from the Triassic Stubensandstein of Germany...
, but these animals were much smaller than Smok. It was one of the largest archosaurs in the world during the Late Triassic, and larger archosaurs did not appear until after the Early Jurassic. Smok lived alongside small carnivorous dinosauromorph and poposauroid archosaurs and large herbivorous dicynodonts.