Casineria
Encyclopedia
Casineria was a tetrapod
which lived 340 million years ago in the Mississippian
epoch. Casineria was a small animal with a total length estimated to have been 15 centimeters. It lived in what was then a fairly dry environment in Scotland. It is noted for its mix of primitive (amphibian) and advanced (reptilian) characters, putting it at or very near the origin of the amniote
s. The sole find is lacking key elements (most of the skull and the whole lower body is missing), making exact analysis is difficult.
Its name, Casineria, is a latinization of Cheese Bay, the site near Edinburgh, where it was found.
in Edinburgh while researchers focused on other projects. Around 1997, work began to expose the remainder of the fossil from the surrounding matrix. The work revealed that the animal probably lived in an environment much drier than previously understood. The findings were first reported in the April 8, 1999 edition of Nature.
groups like Seymouriamorpha
and Diadectomorpha
, Casineria also shows features that ties it in with early reptiles, notably a generally gracile build with light leg-bones, unfused ankles and toes terminating in claws. This would enable the animal to use their feet actively in traction, rather than as holdfasts, and indication of a primarily terrestrial lifestyle. These traits shows it was more closely related to amniote
s than to other known reptiliomorph
amphibians.
With its advanced features, Casineria may have been one of the very first true amniote
s, and thus the first reptile
under traditional classification. In phylogenetic
parlance it would have been a stem amniote, close to, but outside the crown group
Amniota (a group containing the last common ancestor of synapsids and sauropsids and all its descendants). Casineria pushes back the origin of amniote lineages much farther than was previously realized.
. This earliest amniote had five fingers with claws on each hand, and marks the earliest clawed foot. Claws being an intimately bound to the formation of keratin
ous scales in reptiles, Casineria would in life in all likelihood bear scaly, reptilian type skin. In life, it would resemble a small lizard.
Likely being among the first amniote
s in the biological sense, it would have laid amniotic egg
not dependent on being laid in water to survive, possibly hiding them in damp vegetation or hollowed out tree stumps. This has been inferred from the fact that Casineria was found in rocks showing a rather dry environment. In the early Carboniferous period before the appearance of Casineria, vertebrates were primarily aquatic, only spending part of their time on land. Casineria and its relatives were the first vertebrates to live and reproduce on land.
Tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
which lived 340 million years ago in the Mississippian
Mississippian (geologic period)
The Mississippian is a subperiod in the geologic timescale or a subsystem of the geologic record. It is the earliest/lowermost of two subperiods of the Carboniferous period lasting from roughly 359 to 318 Ma...
epoch. Casineria was a small animal with a total length estimated to have been 15 centimeters. It lived in what was then a fairly dry environment in Scotland. It is noted for its mix of primitive (amphibian) and advanced (reptilian) characters, putting it at or very near the origin of the 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...
s. The sole find is lacking key elements (most of the skull and the whole lower body is missing), making exact analysis is difficult.
Its name, Casineria, is a latinization of Cheese Bay, the site near Edinburgh, where it was found.
Discovery
In 1992, an amateur fossil collector spotted the remnants of this four-legged creature on the shore of Cheese Bay, Scotland. For the next five years, the fossil languished at the National Museums of ScotlandNational Museums of Scotland
National Museums Scotland is the organization that runs several national museums of Scotland. It is one of the country's National Collections, and holds internationally important collections of natural sciences, decorative arts, world cultures, science and technology, and Scottish history and...
in Edinburgh while researchers focused on other projects. Around 1997, work began to expose the remainder of the fossil from the surrounding matrix. The work revealed that the animal probably lived in an environment much drier than previously understood. The findings were first reported in the April 8, 1999 edition of Nature.
Phylogenetic relationship
While retaining a general build like those found in the amphibian reptiliomorphReptiliomorpha
Reptiliomorpha refers to an order or subclass of reptile-like amphibians, which gave rise to the amniotes in the Carboniferous. Under phylogenetic nomenclature, the Reptiliomorpha includes their amniote descendants though, even in phylogenetic nomenclature, the name is mostly used when referring to...
groups like Seymouriamorpha
Seymouriamorpha
Seymouriamorpha were a small but widespread group of reptiliomorphs. Many seymouriamorphs were terrestrial or semi-aquatic. However, aquatic larvae bearing external gills and grooves from the lateral line system has been found, making them unquestionably amphibians. The adults were terrestrial...
and Diadectomorpha
Diadectomorpha
Diadectomorpha are a clade of large reptile-like amphibians that lived in Euramerica during the Carboniferous and Early Permian periods, and are very close to the ancestry of the Amniota. They include both large carnivorous and even larger herbivorous forms, some semi-aquatic and others fully...
, Casineria also shows features that ties it in with early reptiles, notably a generally gracile build with light leg-bones, unfused ankles and toes terminating in claws. This would enable the animal to use their feet actively in traction, rather than as holdfasts, and indication of a primarily terrestrial lifestyle. These traits shows it was more closely related to 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...
s than to other known reptiliomorph
Reptiliomorpha
Reptiliomorpha refers to an order or subclass of reptile-like amphibians, which gave rise to the amniotes in the Carboniferous. Under phylogenetic nomenclature, the Reptiliomorpha includes their amniote descendants though, even in phylogenetic nomenclature, the name is mostly used when referring to...
amphibians.
With its advanced features, Casineria may have been one of the very first true 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...
s, and thus the first reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
under traditional classification. In phylogenetic
Phylogenetic nomenclature
Phylogenetic nomenclature or phylogenetic taxonomy is an alternative to rank-based nomenclature, applying definitions from cladistics . Its two defining features are the use of phylogenetic definitions of biological taxon names, and the lack of obligatory ranks...
parlance it would have been a stem amniote, close to, but outside the crown group
Crown group
A crown group is a group consisting of living representatives, their ancestors back to the most recent common ancestor of that group, and all of that ancestor's descendants. The name was given by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms...
Amniota (a group containing the last common ancestor of synapsids and sauropsids and all its descendants). Casineria pushes back the origin of amniote lineages much farther than was previously realized.
Casineria in life
Casineria was an insectivoreInsectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
. This earliest amniote had five fingers with claws on each hand, and marks the earliest clawed foot. Claws being an intimately bound to the formation of keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
ous scales in reptiles, Casineria would in life in all likelihood bear scaly, reptilian type skin. In life, it would resemble a small lizard.
Likely being among the first 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...
s in the biological sense, it would have laid amniotic egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
not dependent on being laid in water to survive, possibly hiding them in damp vegetation or hollowed out tree stumps. This has been inferred from the fact that Casineria was found in rocks showing a rather dry environment. In the early Carboniferous period before the appearance of Casineria, vertebrates were primarily aquatic, only spending part of their time on land. Casineria and its relatives were the first vertebrates to live and reproduce on land.