Other Early Tetrapod Projects
TW:eed Project
Tetrapod World: early evolution and diversification
The TW:eed Project team published a paper in Nature Ecology and Evolution describing the new tetrapod material
discovered in the Tournaisian of south-eastern Scotland (Clack et al. 2016, online version). We described and named five new taxa, noted and figured further
specimens representing at least 7 more, and examined their phylogenetic and ecological context.
Phylogenetically, they spread out across the tetrapod family tree with some closer to Devonian forms, some among
the stem tetrapods of the later Carboniferous, and some even among crown group tetrapods. We estimate the origin
of the crown group to be around 355 Ma, so our findings are in line with recent molecular anaylses.
The new taxa are Koilops herma, Perittodus apsconditus, Ossirarus kierani, Diploradus austiumensis, and Aytonerpeton microps.
The Ballagan Formation, in which they were found, represents a series of flood plain deposits with a mosaic of environments, alternating between land surface and standing freshwater, with occasional marine incursions. Conditions varied over shorter time scales, but were relatively stable over longer ones, the Ballagan Formation representing the first 10-12 million years of the Carboniferous. This mix of environments could have allowed tetrapods to acquire terrestrial capabilities gradually over time.
Two papers on one particular bed from the coastal exposure at Burnmouth described the fauna and environments of tetrapods and other vertebrates, Otoo et al. (2018) and Clack et al. (in press). Both document the presence of rhizodont fishes, lungfish and tetrapods, including a partial jaw of a Crassigyrinus-like animal (Clack et al. 2018a).
Papers describing the sedimentology of the Ballagan Formation have also been published ( Bennett et al., 2016, Kearsey et al. 2016, Millward et al. 2018) and others will appear soon.
A group of us, including Marcello Ruta, Tim Smithson and Andrew Milner, have redescribed it from high-resolution micro-CT scans. Its head is about 12 mm long, it has a long vertebral column with two centra per vertebra, it is limbless, and the teeth show heterodonty (a mixture of tooth types) and durophagy (adaptations to eating hard material). This seems to be the earliest example of such dental modifications among tetrapods, and was probably used for eating material such as small crustaceans or ostracods. Its age has been determined by John Marshall from examination of fossil spores (palynology) as probably around the boundary between the Early and Late Carboniferous, known as Pendleian. This fits with an origin from Loanhead.
The new description was published in Royal Society Open Science journal in 2019 (see my Publications page on this website), and a laymans' summary can be found on the TW:eed project web site ( http://www.tetrapods.org) under 'Outreach: Publication Summaries'.
The new taxa are Koilops herma, Perittodus apsconditus, Ossirarus kierani, Diploradus austiumensis, and Aytonerpeton microps.
The Ballagan Formation, in which they were found, represents a series of flood plain deposits with a mosaic of environments, alternating between land surface and standing freshwater, with occasional marine incursions. Conditions varied over shorter time scales, but were relatively stable over longer ones, the Ballagan Formation representing the first 10-12 million years of the Carboniferous. This mix of environments could have allowed tetrapods to acquire terrestrial capabilities gradually over time.
Two papers on one particular bed from the coastal exposure at Burnmouth described the fauna and environments of tetrapods and other vertebrates, Otoo et al. (2018) and Clack et al. (in press). Both document the presence of rhizodont fishes, lungfish and tetrapods, including a partial jaw of a Crassigyrinus-like animal (Clack et al. 2018a).
Papers describing the sedimentology of the Ballagan Formation have also been published ( Bennett et al., 2016, Kearsey et al. 2016, Millward et al. 2018) and others will appear soon.
Acherontiscus caledoniae
A group of us, including Marcello Ruta, Tim Smithson and Andrew Milner, have redescribed it from high-resolution micro-CT scans. Its head is about 12 mm long, it has a long vertebral column with two centra per vertebra, it is limbless, and the teeth show heterodonty (a mixture of tooth types) and durophagy (adaptations to eating hard material). This seems to be the earliest example of such dental modifications among tetrapods, and was probably used for eating material such as small crustaceans or ostracods. Its age has been determined by John Marshall from examination of fossil spores (palynology) as probably around the boundary between the Early and Late Carboniferous, known as Pendleian. This fits with an origin from Loanhead.
The new description was published in Royal Society Open Science journal in 2019 (see my Publications page on this website), and a laymans' summary can be found on the TW:eed project web site ( http://www.tetrapods.org) under 'Outreach: Publication Summaries'.
Pederpes finneyae
The first complete skeleton of a tetrapod from the earliest
Carboniferous to be described.
This specimen shows the earliest example of a foot adapted for walking on land. It fits in the middle of the temporal, morphological and phylogenetic gap that separates the aquatic Devonian tetrapods from the terrestrial ones of the mid-Carboniferous. See Nature 418.
My student Jon Jeffery made a collecting trip to the basement of the Hunterian Museum in 1996 to look for rhizodonts in furtherance of his PhD on that group of Carboniferous fishes. Among other specimens, he brought to the lab a largish nodule of something that 'looked interesting', allegedly a rhizodont, but he wasn't sure. We looked at it for a few moments, and then I noticed comma-shaped scales across the base of some of the sections. Then some larger plates and cross-sections of bone at the far end of the animal. This was no fish, but a tetrapod, and there were its hind legs and pelvis! The label said 'Calciferous Sandstone Series', which I knew to be Lower Carboniferous, though I wasn't sure how low.
I sent a sample to John Richardson at the Natural History Museum and he confirmed it as Late Tournaisian. What we had was - at that time - the only articulated tetrapod specimen from the Tournaisian yet discovered - the next earliest tetrapod after the Late Devonian, and the only tetrapod specimen from the Lower Carboniferous of Western Scotland.
The specimen was discovered in 1970 by Peder Aspen, after whom it is named. Labelled as a rhizodont, it had escaped detection by me and all of my early tetrapod colleagues who had trawled through the Hunterian's collections, and also by Stan Wood, who had worked in the Hunterian in the early 1970's.
After four years, the specimen was more or less completely prepared, and turned out to be similar in some ways to the primitive tetrapod Whatcheeria from the Viséan of Iowa, described by Lombard and Bolt in 1995. But it is not the same animal, and has some key differences. They have been placed into the clade called Whatcheeriida, which appears to have had a wide distribution in time and space, and may even cross the Devonian/Carboniferous boundary (see Daeschler et al. 2009 in the publications list.)
This specimen shows the earliest example of a foot adapted for walking on land. It fits in the middle of the temporal, morphological and phylogenetic gap that separates the aquatic Devonian tetrapods from the terrestrial ones of the mid-Carboniferous. See Nature 418.
My student Jon Jeffery made a collecting trip to the basement of the Hunterian Museum in 1996 to look for rhizodonts in furtherance of his PhD on that group of Carboniferous fishes. Among other specimens, he brought to the lab a largish nodule of something that 'looked interesting', allegedly a rhizodont, but he wasn't sure. We looked at it for a few moments, and then I noticed comma-shaped scales across the base of some of the sections. Then some larger plates and cross-sections of bone at the far end of the animal. This was no fish, but a tetrapod, and there were its hind legs and pelvis! The label said 'Calciferous Sandstone Series', which I knew to be Lower Carboniferous, though I wasn't sure how low.
I sent a sample to John Richardson at the Natural History Museum and he confirmed it as Late Tournaisian. What we had was - at that time - the only articulated tetrapod specimen from the Tournaisian yet discovered - the next earliest tetrapod after the Late Devonian, and the only tetrapod specimen from the Lower Carboniferous of Western Scotland.
The specimen was discovered in 1970 by Peder Aspen, after whom it is named. Labelled as a rhizodont, it had escaped detection by me and all of my early tetrapod colleagues who had trawled through the Hunterian's collections, and also by Stan Wood, who had worked in the Hunterian in the early 1970's.
After four years, the specimen was more or less completely prepared, and turned out to be similar in some ways to the primitive tetrapod Whatcheeria from the Viséan of Iowa, described by Lombard and Bolt in 1995. But it is not the same animal, and has some key differences. They have been placed into the clade called Whatcheeriida, which appears to have had a wide distribution in time and space, and may even cross the Devonian/Carboniferous boundary (see Daeschler et al. 2009 in the publications list.)
East Kirkton Project
In collaboration with Marcello Ruta, I am in the process of reworking the East Kirkton
'anthracosaur' taxa and the stem amniote Westlothiana. Our study of Silvanerpeton has
been published (Ruta and Clack 2006) and we
are currently working on Eldeceeon.
Additional specimens, combined with much greater experience of working with the problematic East Kirkton preservation, has allowed us to make out much more detail about Silvanerpeton than was previously possible, and we hope to do the same for the other taxa.
Additional specimens, combined with much greater experience of working with the problematic East Kirkton preservation, has allowed us to make out much more detail about Silvanerpeton than was previously possible, and we hope to do the same for the other taxa.
Eucritta melanolimnetes - "beautiful creature from the black lagoon" -
is a creature of mixed affinities - where does it belong? Is it a temnospondyl, an
anthracosaur, a baphetid, or all three? Phylogenetic analysis suggested it was a
basal baphetid (Clack 1998, 2001.)
I am working on a chapter on East Kirkton for a book on terrestrial lagerstätten to be published by Dunedin in Scotland. It will feature, in colour, some previously unfigured specimens as well as those that have already been described.
I am working on a chapter on East Kirkton for a book on terrestrial lagerstätten to be published by Dunedin in Scotland. It will feature, in colour, some previously unfigured specimens as well as those that have already been described.
Chroniosuchians
Jozef Klembara of Bratislava, and I have described a uniquely complete specimen
belonging to the enigmatic group known as chroniosuchians: Chroniosaurus
dongusensis. We were also able to study related material in Moscow. We were
able to produce completely new reconstructions of the skull roof, the braincase,
the vertebral column and limbs, and the palate
(Clack and Klembara 2009,
Klembara et al. 2010). This group of animals
is known from the Late Permian and Early Triassic, with most specimens coming
from Russia. Recently, though, specimens have been found in China and Germany,
suggesting that they were much more widely distributed than previously appreciated.
They have long been associated with anthracosaurs, and indeed the braincase material that we described shows remarkable similarities to those of embolomeres, a sub-group of anthracosaurs, and in particular to the Lower Permian form Archeria from North America. Our phylogenetic analysis could not definitively resolve their position, though they always fell close to embolomeres, along with Silvanerpeton and Gephyrostegus.
The group seems to have both aquatic and terrestrial adaptations, as attested by the rows of interdigitating dermal scutes running above the neural spines, as in some terrestrial dissorophoid temnospondyls and some crocodilians.
They have long been associated with anthracosaurs, and indeed the braincase material that we described shows remarkable similarities to those of embolomeres, a sub-group of anthracosaurs, and in particular to the Lower Permian form Archeria from North America. Our phylogenetic analysis could not definitively resolve their position, though they always fell close to embolomeres, along with Silvanerpeton and Gephyrostegus.
The group seems to have both aquatic and terrestrial adaptations, as attested by the rows of interdigitating dermal scutes running above the neural spines, as in some terrestrial dissorophoid temnospondyls and some crocodilians.
Platyrhinops
In 2009, Andrew Milner and I finally finished a study of Platyrhinops lyelli that we
started in 1984. Platyrhinops is a small amphibamid dissorophoid temnospondyl from the
Late Carboniferous, found in Nyrany, Czech Republic and Linton Ohio. We have, for the first
time, described its skull in detail, including a range of sizes from about 13 - 60 mm skull
length. Platyrhinops, like several other recently described amphibamids, shows some
characters in which it resembles frogs, and its description will add much needed information
to the current debate on the phylogenetic relationships of dissorphoids and their relation to
amphibian origins. The work was published in Transactions of the Royal Society of
Edinburgh (Clack and Milner 2010).
Morphometric Studies
A study in collaboration with Chuck Kimmel and Brian Sidlauskas, I published a paper examining
the relative proportions of the palate in a range of early tetrapod taxa using a variety of
morphometric and statistical techniques (
Kimmel et al.2009).
What appear to be effects of
developmental constraint and/or paeodmorphosis were detected in the phylogenetic trajectories
of vomer:pterygoid length and the size, presence or absence of the ectopterygoid.
Kyrinion martilli, a new baphetid
A new specimen of a baphetid, a primitive type of Carboniferous tetrapod
(once known as a loxommatid).
Palaeontologist Dr Dave Martill was taking a walk along the beach at Whitley Bay, Tyne and Wear, UK, when he tripped on a rock. Being a palaeontologist, he recognised it as something interesting, possibly even a skull, so he deposited it in the Hancock Museum in Newcastle upon Tyne. The specimen turned out to be a complete three dimensional skull of what used to be called a 'loxommatid', now called a baphetid. These are primitive tetrapods from the Carboniferous period, whose skulls are fairly common in coal deposits,though the rest of their bodies are barely known. The Hancock Museum has one of the world's best collections of them. The skull belongs to a new genus and species, published in 2003 in the Canadian Journal of Earth Sciences. This specimen has a beautifully preserved, almost uncrushed occiput, and both stapes are in place.
Palaeontologist Dr Dave Martill was taking a walk along the beach at Whitley Bay, Tyne and Wear, UK, when he tripped on a rock. Being a palaeontologist, he recognised it as something interesting, possibly even a skull, so he deposited it in the Hancock Museum in Newcastle upon Tyne. The specimen turned out to be a complete three dimensional skull of what used to be called a 'loxommatid', now called a baphetid. These are primitive tetrapods from the Carboniferous period, whose skulls are fairly common in coal deposits,though the rest of their bodies are barely known. The Hancock Museum has one of the world's best collections of them. The skull belongs to a new genus and species, published in 2003 in the Canadian Journal of Earth Sciences. This specimen has a beautifully preserved, almost uncrushed occiput, and both stapes are in place.
Crassigyrinus scoticus
This large, fearsome predator from the Viséan of Scotland is known from about
five main specimens. It had the most horrendous bite. Its long, deep skull
was attached to an elongate skeleton with reduced limbs. The forelimb was 'ridiculously
small' (Panchen 1985). Its peculiar nose puzzled palaeontologists for decades, but
newly prepared material helped sort it out. The tiny headless skeleton in its mouth
is a reconstruction of Casineria kiddi drawn to the same scale.
We have recently discovered a partial lower jaw identifiable as a close relative of Crassigyrinus (probably the same genus) in the Tournaisian rocks of Burnmouth (see Smithson et al. 2012), giving the genus a long time-range (see the Romer's Gap Project page.)
We have recently discovered a partial lower jaw identifiable as a close relative of Crassigyrinus (probably the same genus) in the Tournaisian rocks of Burnmouth (see Smithson et al. 2012), giving the genus a long time-range (see the Romer's Gap Project page.)
Casineria kiddi
Until the discovery of Pederpes, and more recently a pentadactyl foot
from the Tournaisian of Scotland, this little skeleton, from the
mid-Viséan of Scotland,
was the earliest known terrestrially adapted skeleton.
Unfortunately the head is not preserved.
A very early examply of pentadactyly, the manus shows evidence of grooves on the planar surface of the phalanges for ligaments that suggest the ability to grasp (see Paton et al. 1999.)
A very early examply of pentadactyly, the manus shows evidence of grooves on the planar surface of the phalanges for ligaments that suggest the ability to grasp (see Paton et al. 1999.)
Pholiderpeton scutigerum
My PhD animal was an embolomere - a Carboniferous crocodile-analogue. From Bradford,
UK, the specimen gave us the first anthracosaur stapes.
Evolution of the ear in tetrapods
Following from the discovery of the stapes of Pholiderpeton, I have continued my
interest
in the evolution of tetrapod hearing in a series of papers. The stapes of early tetrapods,
including Acanthostega, have provided key information about the evolution of the tetrapod
ear. This also ties in with an interest in braincase evolution.
See Clack 1997, 2002.)
Last updated 7th June, 2019 by
Rob Clack