Petrolacosaurus
Encyclopedia
Petrolacosaurus was a small, 40 centimetres (15.7 in) long, reptile, and the earliest diapsid
known. It lived during the late Carboniferous
period, the Joggins strata where it was found are dated to 302 million years old.
The prehistoric reptile's diet may have consisted mainly of small insect
s. Petrolacosaurus had distinctive canine-like secondary-sized teeth, a trait found primarily in therapsids, and later in mammals. Its fossils were found in Kansas
, USA.
television show Walking with Monsters
. The animal is incorrectly used as an example of an ancestral amniote
, or a "reptile" in the traditional Linnaean sense of the word. From an evolutionary point of view, this means that Petrolacosaurus was used to illustrate the first vertebrates which were already fully adapted to terrestrial life, but were still cold-blooded. It was portrayed as living alongside several species of giant arthropods, like giant mesothelae
spiders, and Meganeura
, a giant dragonfly
, as well as anthracosaur amphibians like Proterogyrinus
. In accordance with its use as a proto-amniote, Petrolacosaurus is portrayed as the common ancestor of both synapsids such as Dimetrodon
, including mammals, and sauropsids, including modern reptiles and birds; it is also stated that its heart was the template for our own.
While Petrolacosaurus was indeed a relatively early amniote and was typically lizard
-like, as were all the first amniotes, it was nevertheless too derived to be portrayed as the ancestor of all modern forms. In fact, it was already a diapsid, with two openings known as "temporal fenestrae" on each side of its skull to add attachment points for jaw muscles. Hence, it cannot have been the ancestor of any synapsids, which have only one such opening and diverged from the common amniote tree before the diapsids did.
Diapsid
Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...
known. It lived during the late Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
period, the Joggins strata where it was found are dated to 302 million years old.
The prehistoric reptile's diet may have consisted mainly of small insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s. Petrolacosaurus had distinctive canine-like secondary-sized teeth, a trait found primarily in therapsids, and later in mammals. Its fossils were found in Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
, USA.
In popular culture
Petrolacosaurus was featured in the BBCBBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
television show Walking with Monsters
Walking with Monsters
Walking with Monsters is a three-part British documentary film series about life in the Paleozoic, bringing to life extinct arthropods, fish, amphibians, synapsids, and reptiles...
. The animal is incorrectly used as an example of an ancestral amniote
Amniote
The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...
, or a "reptile" in the traditional Linnaean sense of the word. From an evolutionary point of view, this means that Petrolacosaurus was used to illustrate the first vertebrates which were already fully adapted to terrestrial life, but were still cold-blooded. It was portrayed as living alongside several species of giant arthropods, like giant mesothelae
Mesothelae
The Mesothelae are a suborder of spiders that includes the extinct families Arthrolycosidae and Arthromygalidae and the only extant family Liphistiidae....
spiders, and Meganeura
Meganeura
Meganeura is a genus of extinct insects from the Carboniferous period approximately 300 million years ago, which resembled and are related to the present-day dragonflies. With wingspans of more than 75 cm , M. monyi is one of the largest known flying insect species; the Permian Meganeuropsis...
, a giant dragonfly
Dragonfly
A dragonfly is a winged insect belonging to the order Odonata, the suborder Epiprocta or, in the strict sense, the infraorder Anisoptera . It is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body...
, as well as anthracosaur amphibians like Proterogyrinus
Proterogyrinus
Proterogyrinus was an anthracosaur, a large group of reptilian reptiliomorphs. It is likely that the first reptiles, such as Petrolacosaurus, evolved from reptilomorphs...
. In accordance with its use as a proto-amniote, Petrolacosaurus is portrayed as the common ancestor of both synapsids such as Dimetrodon
Dimetrodon
Dimetrodon was a predatory synapsid genus that flourished during the Permian period, living between 280–265 million years ago ....
, including mammals, and sauropsids, including modern reptiles and birds; it is also stated that its heart was the template for our own.
While Petrolacosaurus was indeed a relatively early amniote and was typically lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
-like, as were all the first amniotes, it was nevertheless too derived to be portrayed as the ancestor of all modern forms. In fact, it was already a diapsid, with two openings known as "temporal fenestrae" on each side of its skull to add attachment points for jaw muscles. Hence, it cannot have been the ancestor of any synapsids, which have only one such opening and diverged from the common amniote tree before the diapsids did.