''Dendrerpeton'' (from el, δένδρον , 'tree' and el, ἑρπετόν , 'creeping thing') is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of an extinct group of temnospondyl amphibians. Its

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s have been found primarily in the

Joggins Formation The Joggins Formation is a geologic formation in Nova Scotia. It preserves fossils dating back to the Carboniferous period, including ''Hylonomus'', the earliest known reptile. In addition to fossils, the Joggins Formation was a valuable source of ...

of Eastern

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

and in

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

. It lived during the Carboniferous and is said to be around 309–316 million years of age, corresponding to more specifically the

Westphalian (stage) The Westphalian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 313 and 304 Ma (million years ago). It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Westpha ...

age. Of terrestrial temnospondyl amphibians

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

, it represents the first stage. Although multiple

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

have been proposed, the species unanimously recognized is ''D. acadianum''. This species name comes from “Acadia” which is a historical name for the

Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...

region as a French colony. It refers to the location of the coal field at which the fossil was found.

History and discovery

The majority of ''Dendrerpeton'' fossils that had been discovered were disarticulated due to the way in which they had formed. They are often associated with

Lycopod Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...

Sigillaria ''Sigillaria'' is a genus of extinct, spore-bearing, arborescent (tree-like) plants. It was a lycopodiophyte, and is related to the lycopsids, or club-mosses, but even more closely to quillworts, as was its associate ''Lepidodendron''. Fossil ...

, and Calamite tree stumps which decayed inside and became hollow, and are found in Parrsboro formation and the

Joggins formation The Joggins Formation is a geologic formation in Nova Scotia. It preserves fossils dating back to the Carboniferous period, including ''Hylonomus'', the earliest known reptile. In addition to fossils, the Joggins Formation was a valuable source of ...

. There is also evidence for articulated specimens in

at the Jarrow Colliery. However, they were found to be enveloped by substance that had a very low pH. Although not all specimens were equally affected and some were well preserved, many were not because of this pH. In general, many of the fossils are found in the trunks of these trees or coal swamps. In 1861 one of the first skeleton of ''Dendrerpeton'' ''acadianum'' almost in its entirety was discovered by J.W. Dawson at the South of Joggins, Nova Scotia. It was part of the trunk of a tree, and likely this trunk in which the animal had been was about four feet deep. The skeleton however remained because the bark was preserved due to coal that was

bituminous Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...

. In 1998 came the first skeleton of ''Dendrerpeton'' ''acadianum'' that was nearly completely articulated, again from the Joggins of Nova Scotia. It was essentially undisturbed, and in this case was not associated with a tree but instead with a boulder found at a beach. This specimen provided the opportunity for a deeper understanding of the skeleton of this taxon because of its three-dimensionality and the detail preserved.

Paleoenvironment and Geology

Generally, the distribution of ''Dendrerpeton'' is rather concentrated in the region of Nova Scotia, Canada, more specifically many specimen were found in the

. However, there are also fossils indicating the animals presence in Ireland. In Ireland the environment consisted heavily of coal swamps

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s which are found in the Carboniferous. These coal swamps were also found in Nova Scotia, as well as cliffs along the coast. There often are erosions happening in this region with the many cliffs. Also present are strata that drip downwards of the rocks which have been investigated, and the general climate is predicted to lean more humid, but there are times of shift to drier conditions. It has been predicted that the environment at the time could have undergone fires, which was discovered through the examination of fossil charcoal. This leads to one explanation for the abundance of fossils found within the tree stumps, speaking particularly here about ''Dendrerpeton.'' The occurrence of a fire may have caused them to seek shelter and protection by hiding away into the decayed hollow cores of the trees, as explained by Andrew Scott. However, it is also explained that rather than escaping to the trees by choice, they get trapped. This works particularly for terrestrial animals such as ''Dendrerpeton,'' however other taxa are also found and there is evidence of their survival within these stumps for some period of time, proven by the presence of coprolitic material preserved in the fossils.

Temnospondyls Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carbo ...

are said to be found from the Carboniferous to the middle-Cretaceous, and ''Dendrerpeton'' considered to be of the earliest or base of the temnospondyls indicating its existence primarily during the Carboniferous.

Description

The length of ''Dendrerpeton'' is approximately 35 cm in length according to the measurements done on the nearly fully articulated skeleton, keeping in mind that there was a short portion of the tail posteriorly missing. Additionally, had stated that the maximum length could be up to a

meter The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its pref ...

Skull and Skeleton

The length of the skull can range from 84mm to 104mm for midline length. to Through the analysis of the middle

ear An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of ...

region of ''Dendrerpeton acadianum'', it could be determined that this

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

has a tympanic ear that is not there as a means of support for the

palatoquadrate In some fishes, the palatoquadrate is the dorsal component of the mandibular arch, the ventral one being Meckel's cartilage. The palatoquadrate forms from splanchnocranium in various chordates including placoderms and acanthodians. See also * ...

, but rather the positioning of the

stapes The ''stapes'' or stirrup is a bone in the middle ear of humans and other animals which is involved in the conduction of sound vibrations to the inner ear. This bone is connected to the oval window by its annular ligament, which allows the foo ...

indicates that it is used for the movement of sound. This

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

demonstrates ''Dendrerpeton'' having a hearing system that mimics that of

anurans A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...

. This was contrary to what was previously thought, which was that it had a "squamosal embayment" rather than an otic notch. However, an otic notch can now be considered a feature of this taxa. Also present are interpterygoid , and a pair of palatal tusks within the vomer which lay medially to the internal naris. Palatal tusk pairs can also be found the ectopterygoid and the palatine. As for the lower jaw, if the animal catches prey it is able to get it to the denticulate

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 separ ...

because compression of the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

s is not

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction * Lateral cricoarytenoid muscle * Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral co ...

along their length. The dentary of the lower jaw was found to be the biggest of all the mandibular parts. There also looked to be approximately 40–50 teeth found on each jaw side (in the upper jaw including both the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has ...

and

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...

), the marginal teeth. With these teeth ''Dendrerpeton'' can catch larger

prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

, and was also found to feed on insects which was determined through examination of fossils and presence of insects in the

coal forest Coal forests were the vast swathes of wetlands that covered much of the Earth's tropical land areas during the late Carboniferous ( Pennsylvanian) and Permian times.Cleal, C. J. & Thomas, B. A. (2005). "Palaeozoic tropical rainforests and their e ...

s. The elements of the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

which are on the surface and exposed have s all over. On the dorsal side of the skull and positioned more

posteriorly Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

there is a

foramen In anatomy and osteology, a foramen (;Entry "foramen"
in

Post-cranial skeleton

Within the

vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordate ...

it is noted that the intercentrum is smaller than the rhomboidal paired pleurocentra and the posterior centrum having a

concave Concave or concavity may refer to: Science and technology * Concave lens * Concave mirror Mathematics * Concave function, the negative of a convex function * Concave polygon, a polygon which is not convex * Concave set * The concavity of a ...

shape that will meet with the next intercentrum. The notochord was encompassed by a thickened wall formed by the intercentra. With examination it was also found that a long tail was not likely present in this animal. In regards to the

ribs The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a semi- ...

, they are generally short and

costal cartilage The costal cartilages are bars of hyaline cartilage that serve to prolong the ribs forward and contribute to the elasticity of the walls of the thorax. Costal cartilage is only found at the anterior ends of the ribs, providing medial extension. ...

appears to have once been present because of swelling that is found where the end of the shaft is.

Classification

''Dendrerpeton'' is the

of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Dendrerpetondtidae which contains both '' Balanerpeton'' and ''Dendrerpeton''. It is part of the order

Temnospondyli Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carb ...

. Although it is most commonly known for the species ''D. acadianum,'' there have also been other species names proposed. However, there seems to be discussion on whether any of them are valid enough to distinguish as a separate species of their own. An example of one of these species is ''Dendrerpeton oweni'', which Robert Carroll claimed had no particular distinguishable feature and looked to be simply ''Dendrerpeton acadianum'' but smaller because it is of younger age.