Loxommatidae
Encyclopedia
Baphetidae is an extinct family
of early tetrapod
s. Baphetids were large labyrinthodont
predators of the Late Carboniferous
period (Namurian
through Westphalian
) of Europe. Fragmentary remains from the Early Carboniferous of Canada have been tentatively assigned to the group. The phylogenetic relationships of baphetids is uncertain; while many studies have placed the group as a close relative of Amniota, other analyses have found Baphetidae to be a more basal clade of early stem tetrapod
s. Baphetids were among the first of the Carboniferous fossil tetrapod
s to be found and were originally described in 1850 by William Dawson
. The baphetids have been referred to the family Loxommatidae, but this group was later shown to be a junior synonym of Baphetidae, which was named earlier in 1865. Baphetids are known mainly from skulls; very little skeletal material has been found.
show that most were fish-eaters. Their development were likely amphibian
, though no larval fossils are known. Their best-known characteristic was a curious, keyhole-shaped orbit formed by excavation of the lacrimal
and prefrontal
bones in front of the eye. It has been suggested that this space accommodated a salt gland or some kind of electrosensory organ. Perhaps the better hypothesis is that the space allowed room for the contraction of an enlarged pterygoideus muscle. In that case, this skull modification would represent an early form of skull fenestration for jaw muscles.
The skull is shallow. Unlike the better-known embolomeres
, the baphetid cheek and skull roof
are sutured together. There is a strongly embayed spiracular ("otic") notch, but the stapes is distally broad, which seems to rule out a sensitive hearing apparatus. The palate is closed -- a primitive character, but very different from the temnospondyls
. The coronoids bear no teeth or denticles, while the dentary has a double tooth row.
Since the taxon is based almost exclusively on skulls, the body is very poorly known. It is often said that the body was crocodile-like, but this appears to be largely supposition.
It is not clear whether all of the genera assigned to this group are really closely related. The traditional four genera of baphetids (Loxomma
, Baphetes
, Megalocephalus
, and Spathicephalus
) have recently been supplemented by Eucritta
, a somewhat different form. It has also been suggested that Crassigyrinus
may be closely related.
when he erected the family Baphetidae in 1865 for Baphetes. Richard Lydekker
named Loxomatinae in 1889 for Loxomma, which later became known as Loxommatidae. D. M. S. Watson described the group as Loxommidae in 1917. Later studies have shown Baphetes and Loxomma to be close relatives within the same family, and because Baphetidae was named before Loxommatidae, it has seniority and is the valid name of the group.
(reptile-like amphibia). It is likely, however, that they represent one more of a number of early Carboniferous tetrapodomorph radiations. Computer-assisted phylogenetic analyses
of a data matrix using characteristics of most of the major groups of terrestrial vertebrates place the Baphetids close to the ancestry of amniote
s.
With the reinterpretation of the Ichthyostegalia as aquatic forms, baphetids are good candidates for the spot of first labyrinthodont group to actually spend substantial time on land. If so, baphetids may be a rather important taxon.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of early tetrapod
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...
s. Baphetids were large labyrinthodont
Labyrinthodontia
Labyrinthodontia is an older term for any member of the extinct subclass of amphibians, which constituted some of the dominant animals of Late Paleozoic and Early Mesozoic times . The group is ancestral to all extant landliving vertebrates, and as such constitutes an evolutionary grade rather...
predators of 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 (Namurian
Namurian
The Namurian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 326 and 313 Ma . It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Namurian is named for the Belgian city and province of Namur where strata of this age...
through Westphalian
Westphalian
Westphalian may refer to:* The culture or people of the Westphalia region of Germany* Westphalian language, one of the major dialect groups of West Low German* Westphalian sovereignty, a concept in international relations* Westphalian , in geology...
) of Europe. Fragmentary remains from the Early Carboniferous of Canada have been tentatively assigned to the group. The phylogenetic relationships of baphetids is uncertain; while many studies have placed the group as a close relative of Amniota, other analyses have found Baphetidae to be a more basal clade of early stem tetrapod
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...
s. Baphetids were among the first of the Carboniferous fossil tetrapod
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...
s to be found and were originally described in 1850 by William Dawson
William Dawson
-Politicians:* William Johnston Dawson , U.S. Representative from North Carolina* William L. Dawson , U.S. Representative from Illinois* William M. O. Dawson, Governor of West Virginia...
. The baphetids have been referred to the family Loxommatidae, but this group was later shown to be a junior synonym of Baphetidae, which was named earlier in 1865. Baphetids are known mainly from skulls; very little skeletal material has been found.
Palaeobiology
The presence of lateral lines and the long rows of needle-like teethTooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
show that most were fish-eaters. Their development were likely amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
, though no larval fossils are known. Their best-known characteristic was a curious, keyhole-shaped orbit formed by excavation of the lacrimal
Lacrimal bone
The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders.-Lateral or orbital surface:...
and prefrontal
Prefrontal bone
The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls. It first evolved in the sarcopterygian clade Rhipidistia, which includes lungfish and the Tetrapodomorpha. The prefrontal is found in most modern and extinct lungfish, amphibians and reptiles...
bones in front of the eye. It has been suggested that this space accommodated a salt gland or some kind of electrosensory organ. Perhaps the better hypothesis is that the space allowed room for the contraction of an enlarged pterygoideus muscle. In that case, this skull modification would represent an early form of skull fenestration for jaw muscles.
The skull is shallow. Unlike the better-known embolomeres
Embolomeri
The Embolomeri is a suborder of Reptiliomorpha. The Embolomeri first evolved from reptile-like amphibians in the Early Carboniferous...
, the baphetid cheek and skull roof
Skull roof
The skull roof , or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes and all land living vertebrates. The bones are derived from dermal bone, hence the alternative name dermatocranium...
are sutured together. There is a strongly embayed spiracular ("otic") notch, but the stapes is distally broad, which seems to rule out a sensitive hearing apparatus. The palate is closed -- a primitive character, but very different from the temnospondyls
Temnospondyli
Temnospondyli is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent...
. The coronoids bear no teeth or denticles, while the dentary has a double tooth row.
Since the taxon is based almost exclusively on skulls, the body is very poorly known. It is often said that the body was crocodile-like, but this appears to be largely supposition.
It is not clear whether all of the genera assigned to this group are really closely related. The traditional four genera of baphetids (Loxomma
Loxomma
Loxomma is an extinct genus of Loxommatidae. It was first named by Huxley in 1862.-External links:* at the Paleobiology Database....
, Baphetes
Baphetes
Baphetes is an extinct genus of tetrapod. It was first named by Richard Owen in 1854. The type species is B. planiceps.-External links:* in the Paleobiology Database...
, Megalocephalus
Megalocephalus
Megalocephalus is an extinct genus of loxommatid from the late Carboniferous period. Its fossils have been found in China and North America. It contains two species, M. pachycephalus and M. lineolatus. The skull of M. pachycephalus could measure about eight inches long.-External links:* at the...
, and Spathicephalus
Spathicephalus
Spathicephalus is an extinct genus of Loxommatidae.-Sources:* Assembling the Tree of Life by Joel Cracraft and Michael J. Donoghue...
) have recently been supplemented by Eucritta
Eucritta
Eucritta melanolimnetes is an extinct tetrapod from the Carboniferous period of Scotland. Its name is a homage to the 1954 sci-fi/horror movie Creature from the Black Lagoon....
, a somewhat different form. It has also been suggested that Crassigyrinus
Crassigyrinus
Crassigyrinus is an extinct genus of carnivorous stem tetrapod from the Early Carboniferous of Scotland and possibly Greer, West Virginia. The type specimen was originally described as Macromerium scoticum and lacked a complete skull...
may be closely related.
Taxonomy
Baphetids were first described by Edward Drinker CopeEdward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
when he erected the family Baphetidae in 1865 for Baphetes. Richard Lydekker
Richard Lydekker
Richard Lydekker was an English naturalist, geologist and writer of numerous books on natural history.-Biography:...
named Loxomatinae in 1889 for Loxomma, which later became known as Loxommatidae. D. M. S. Watson described the group as Loxommidae in 1917. Later studies have shown Baphetes and Loxomma to be close relatives within the same family, and because Baphetidae was named before Loxommatidae, it has seniority and is the valid name of the group.
Phylogeny
Baphetids have been previously considered primitive temnospondyls and more recently batrachosaursBatrachosauria
Batrachosauria is a name given either to very reptile-like amphibians dating from the Carboniferous and Permian periods, or to amniotes and those amphibians very closely related to them...
(reptile-like amphibia). It is likely, however, that they represent one more of a number of early Carboniferous tetrapodomorph radiations. Computer-assisted phylogenetic analyses
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
of a data matrix using characteristics of most of the major groups of terrestrial vertebrates place the Baphetids close to the ancestry of 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.
With the reinterpretation of the Ichthyostegalia as aquatic forms, baphetids are good candidates for the spot of first labyrinthodont group to actually spend substantial time on land. If so, baphetids may be a rather important taxon.