Paleontologists have described the earliest known animal adapted for life in the treetops, according to a paper in the Proceedings of the Royal Society B, released online today. Jörg Fröbisch, of the Field Museum, and Robert Reisz, from the University of Toronto, found several adaptations for arboreality when they examined fossil skeletons of Suminia getmanovi , a small (20 inches/50 cm) herbivore from the Late Permian of Russia.

The most striking features of the skeleton of Suminia are the relatively large hands and feet. Most of their length is taken up by long, slender fingers and toes tipped with strongly curved, laterally (side-to-side) compressed claws, which are similar in proportion and shape to some modern tree-clinging animals, including dermopterans, megabats, and lizards. The first digits on the hands and feet diverge from the remaining four digits as well, and may have been used as opposable ‘thumbs’ as the animal clung to the branches.

Skeleton of Suminia getmanovi, Paleontological Institute (Moscow) specimen number 2212/116 (spec. 1) Photo by Diane Scott.

More subtle features also point toward arboreal habits. The tail of Suminia is relatively long, and the vertebrae show strong processes halfway down its length. These processes could have supported muscles that allowed Suminia to use its tail for balance or, possibly, as a prehensile grasping organ.

Suminia, at 260,000,000 years old, is the first known vertebrate with this degree of arboreal specialization. Fröbisch and Reisz note that the Late Permian Period, and the Kotel’nich locality where Suminia was found, provides some of the earliest evidence for “modern terrestrial ecosystems with large numbers of plant-eaters supporting few top predators.” While large megaherbivores fed on the greenery below, Suminia found a new way to exploit the foliage in the treetops, taking the first known step into a niche that vertebrates would return to several times over the next 260 million years.

Life restoration of Suminia getmanovi by Christina Stoppa.

Lawless teeth

In part because of some very poorly-written articles and headlines, and in part because talking about vertebrate relationships is just plain enjoyable, it seems like a good place to put in a little bit of context regarding exactly what Suminia is related to.

Suminia is a synapsid, a group of vertebrate animals that would eventually (some 50-100 million years after Suminia) give rise to the ancestors of today’s mammals. Although some synapsids have been called “mammal-like reptiles,” (because they certainly laid eggs and might have looked something like lizards) there are no true reptiles in the synapsid group. All true reptiles—turtles, lizards, snakes, crocodiles—even dinosaurs and birds—belong to a completely separate group.

Among the synapsids, Suminia is considered a therapsid, a phrase commonly used to indicate a grade of synapsid development in between the earlier pelycosaur-grade (think Dimetrodon) and the later mammal-grade. (Although, since mammals evolved from therapsids, we’re technically therapsids too, and since therapsids evolved from pelycosaurs, we can all claim that title as well.)

Among the therapsids, Suminia is an early member of the anomodont (“lawless tooth”) lineage. Sometime during the Early/Middle Permian period, the anomodont line split off from the line of therapsids that would, by way of a whole bestiary of gorgonopsians and therocephalians and countless cynodonts, eventually lead to mammals. The closest relatives we (and all other mammals) share with Suminia would have lived before the Late Permian, around 275,000,000 years ago (give or take several million years) .

The anomodonts have no living descendants, but their roster includes the great radiation of dicynodonts that survived the end-Permian extinction, became some of the largest terrestrial herbivores of the Triassic, and might possibly have survived into the Cretaceous if the identification of an Australian fossil is correct.

Placerias hesternus, a Late Triassic anomodont from Arizona. (Illustration by me, for the day job)

Contrary to what you might have read regarding this discovery, dinosaurs did not evolve from synapsids, and while Suminia is a human relative, this potential predator of Suminia is a much closer relation.

• Reference: Fröbisch, J. and Reisz, R. R. 2009. The Late Permian herbivore Suminia and the early evolution of arboreality in terrestrial vertebrate ecosystems. Proc. Royal Soc. B Published online before print July 29, 2009, doi: 10.1098/rspb.2009.0911.
• Web Coverage:
  • Press Release [ZIP file]
  • BBC News: Fossil is the earliest tree-dweller
  • Laelaps: Suminia: Life in the trees 260 million years ago
  • The Dragon’s Tales: Oldest Known Arboreal Herbivore Found…IN THE PERMIAN!

Some images and info for this post came from this press release.

• Several prime pelycosaur posts from recent field work in the Permian beds of Seymour, including Dimetrodon-as-chondrichthivore and new material that may be from the narrow-snouted finback Secodontosaurus .
• And a step-by-step look at how Julius T. Csotonyi recreated the world of Leonardo, the fantastically well-preserved Brachylophosaurus, for the museum’s Dinosaur Mummy CSI: Cretaceous Science Investigation exhibit. Csotonyi’s digital paintings are about the best I’ve seen, and this post gives valuable insight into his process.

• New Amphibian: Gerobatrachus hottoni
• Name means:Hotton’s Elder Frog
• Relations: Amphibamid temnospondyl and stem-batrachian (an early offshoot on the lineage leading to frogs and salamanders)
• Location: Texas, U.S.A.
• Age: Early Permian, ~290,000,000 years ago
• Size: Less than 12cm (5 inches) long
• Info: The three groups of living amphibians (frogs, salamanders, and caecilians) most certainly had their roots in the great amphibian radiations of the Late Paleozoic Era, but the fossil record has provided few clues that help pinpoint their precise ancestry. Gerobatrachus was a small temnospondyl, part of a very successful and numerous group of amphibians in the latter part of the Paleozoic. The remains of Gerobatrachus exhibit a unique mosaic of features in its teeth, ears, limbs, and vertebrae that suggest it may have been close to the origins of both modern frogs and salamanders. Although many researchers have proposed a close relationship between all three groups of living amphibians, a phylogenetic analysis that included Gerobatrachus found that caecilians had their origins in a completely different group of Paleozoic amphibians, the lepospondyls.
• Reference: Anderson, J. S., Reisz, R. R., Scott, D., Fröbisch, N. B., and Sumida, S. S. 2008. A stem batrachian from the Early Permian of Texas and the origin of frogs and salamanders. Nature 453, 515–518 (22 May 2008) | doi:10.1038/nature06865. The article is available for download from the Center for North American Herpetology PDF Library.
• Web coverage:
  • Press Release
  • LiveScience on MSNBC
  • The Dragon’s Tales 1 & 2
  • Palaeoblog
  • El PaleoFreak

First up, Will at The Dragon’s Tales has had a couple of great articles on two of the more charismatic groups from the latter days of the Paleozoic: the carnivorous, sabre-toothed gorgonopsians and the herbivorous, tusk-beaked dicynodonts. Plus, he notes that there are some fantastic restorations of Permian vertebrates showing up on Wikipedia.

Speaking of dicynodonts, The Lord Geekington, mentions the ubiquitous Permo-Triassic straddler Lystrosaurus in his review of aquatic habits in stem-group synapsids. At the other end (that is, the beginning) of the Permian, he also discusses the potentially piscivorous pelycosaur Ophiacodon.

Finally, I recently came across the Houston Museum of Natural Science’s Prehistoric CSI blog, whose archives are chock full of fossil finds from Seymour, Texas—a treasure trove of Early Permian vertebrates—with videos and photos, and field sketches by Dr. Robert Bakker.

According to Wikipedia, the WIPP site was chosen, in part, because the salt deposits have remained relatively stable since they precipitated from a receding Permian sea, over 250,000,000 years ago. Presumably, the same stability helped preserve the earliest direct evidence of biological life—nearly four times the age of the previous record holder: traces of protein from 68 million year-old T. rex fossils.

Cellulose microfibers, from the UNC News press release.

Cellulose microfibers were the most abundant biological materials found, although the article tantalizingly mentions that some evidence of ancient DNA was “observed.”

Now a quarter-billion year-old bit of biomass is pretty darn nifty, and since the research is published in April’s issue of Astrobiology it leads to some interesting ideas about the possibility of finding durable bio-molecules preserved in salt deposits on other worlds. But I think there’s far greater potential for speculation here. I mean, we’ve got Paleozoic biology in proximity to low-level radiation. Forget the atom-bomb triggered monster ants of THEM!—imagine a pickled monuran, revivified and grotesquely enlarged by the careless placement of a used radiation suit, leaping out across the desert as it attempts to satisfy 250 million years worth of salt-cured hunger…

Deep in southern New Mexico, not far from the city of Las Cruces, lie the Robledo Mountains. Tectonic activity along the Rio Grande Rift pushed up the Robledos during the past 30 million years, but the rocks that make up the mountains are about ten times older. In fact, just about 290 million years ago the most famous rocks of the Robledos were being created as layers of fine-grained mud collected near the shores of an Early Permian sea.

This Permian mud was of a perfect consistency to preserve the imprint of anything that touched its surface—the sharp-clawed tracks of a passing Dimetrodon, ropelike branches fallen from Walchia conifers, impact craters from raindrops—even the footfalls of tiny insects left their marks in the surface. As the mud was buried and hardened into rock, the imprints were preserved within the sandstones and siltstones that today make up the Robledo Mountains. The abundance, diversity, and quality of tracks provide a unique look into an Early Permian ecosystem. And the scientific importance of the site has inspired a grassroots movement campaigning for a Prehistoric Trackways National Monument in the Robledos.

A paper in the latest issue of Palaeontology is a great example of the sort of information coming out of the Robledo Mountains. Nicholas Minter and Simon Braddy describe walking and jumping trackways made by an extinct group of insects and compare their locomotor reportoire to those of their living relatives.

The holotype and paratypes of Tonganoxichnus robledoensis.
Photograph and interpretive line drawing of the trackways.
Scale bar=10mm. This and all subsequent figures from Minter and Braddy 2006.
© Copyright The Palaeontological Association. Reproduced with permission.

The photo and diagram above show the type specimens of the ichnospecies Tonganoxichnus robledoensis. It preserves the imprints made by two small insects as they jumped across the mud, one on the left and one on the right. The trackmakers were travelling from bottom to top in this view, with imprints of legs towards the front and a long abdomen and “tail” trailing behind.

The Paleozoic monuran Dasyleptus.
scale=1mm. From Minter and Braddy 2006.
© The Palaeontological Association

The shape of the tracks is suggests that the trackmaker belonged to a group of insects known as the Archaeognatha, which have simple legs ending in points, long abdomens, and long terminal filaments (“tails”). There are jumping archaeognathans living today called “bristletails” because they possess lateral cerci that give their “tail” a three-pronged appearance. But the Tonganoxichnus tracks show no signs of a bristly tail, and were probably made by an extinct group of archaeognathans called monurans (“one tail”) for what I suspect is an obvious reason.

Trackway of a monuran walking,
then jumping, then walking again.
From Minter and Braddy 2006.
© The Palaeontological Association

Minter and Braddy examined 23 sets of Tonganoxichnus robledoensis trackways and found that the Robledo monurans could travel by means of successive, forward-facing jumps several times their body length. Subtle details in the tracks showed that some of the monurans were pushing off more with their legs, while in others a flexing of the abdomen provided the main propulsive force. There were even a few tracks that suggested the jumper was using both its legs and abdomen to propel itself forward.

A living archaognathan, the bristletail Petrobius brevistylis, has a similar proclivity for jumping, but with a few distinct differences. Petrobius normally progresses by successive, leg-propelled hops about one body-length in distance. But when confronted with a predator, Petrobius switches to a series of confusing, abdomen-propelled jumps that carry it much further, but in an essentially random direction (none of the Tonganoxichnus robledoensis trackways showed any evidence of random jumping).

Petrobius occasionally walks, but only when travelling on the underside of rocks where hopping is problematic. Trackway evidence indicates that the Robledo monurans walked somewhat more regularly. Minter and Braddy note that five specimens of insect-walking trackways (referred to the ichnospecies Stiaria intermedia) either end in a Tonganoxichnus-style jumping trace or begin with a similar landing imprint. One specimen (shown here, travelling from bottom to top) shows where a monuran was walking, jumped a few body-lengths forward, landed on its abdomen, then resumed its stroll. The authors note that similar walking trackways (uninterrupted by jumping traces) are relatively common elements of the Robledo tracksites, suggesting that walking played a greater role in monuran locomotion than it does in their distant, modern relatives.

Minter, N. J. and Braddy, S. J. 2006. Walking and jumping with Paleozoic apterygote insects. Palaeontology 49: 4, 827–835.

Thanks to the Palaeontological Association for granting permission to reproduce figures from the article, and to Nicholas Minter for bringing greater attention to these nifty little tracks. Tip of the toupee to Allan Lerner for sending a copy of the paper my way.

First on the list was a little field trip that I took during the middle of the month. For five days I was out poking about some Pennsylvanian strata in the southwestern corner of New Mexico (in what state residents call “the bootheel”) tagging along with a stratigraphic research team led by NMMNH&S curator Dr. Spencer Lucas.

Here’s where we were working, a nice 1500-foot pile of more-or-less neatly stacked Late Paleozoic strata called New Well Peak. This photo was taken from our campsite at the “new” well, which had long since run dry. But the layers of limestone that made up the peak told a tale of when this now-arid parcel of the Gadsden Purchase lay at the bottom of the sea.

Climbing through the strata we came across bits of crinoids, brachiopods, coral, and sponges. We looked for rocks bearing fusilinids, protozoans that lived on the ancient sea bottoms whose fossils are helpful in determining the age of the rocks. The largest of these looked like petrified grains of rice; the smallest were barely visible. This photo shows some of the larger ones we found:

Two members of the team were looking for conodonts as well, or to be more accurate, were looking for rocks that they might be able to find conodont fossils in. Conodonts are known almost exclusively from microscopic teeth, which make them difficult to find in the field. So they collected bags of rocks from outcrops that looked promising, which will go back to laboratories where the fossils could be chemically teased from the rocks and identified under high-powered microscopes. Although it seems like a lot of work for tiny fossils, conodont tooth morphology changed over time, which makes them useful as markers for different time periods. And when enlarged, they are beautiful little sculptures in their own right.

So, between rock samples, conodont samples, and fusilinids, we each carried a heavy load of rocks off the mountain each day. It was an awfully quick way to realize just how out of shape I’ve gotten since my last field outing, but the fresh air, conversation, and stunning scenery made the stiff shoulders and sore feet well worth it.

By the end of the last day, the excellent meal prepared by Chet, the camp cook, is far more interesting than another typical New Mexico sunset.

I didn’t sketch too much on this trip, but I did get one little watercolor of New Well Peak done:

But I really want to promote Bulletin 31, The Permian of Central New Mexico. As you might guess, this is a smaller, more focused collection of papers, and it reviews the current state of research in New Mexico Permian localities that are still producing fossils after a century of exploration and collecting. Several of the pen-and-ink drawings displayed in our Dispatch from the Permocarboniferous posts are published in this volume, including a nice toothy Eryops on the front cover (the skull that inspired the image is described inside).

The bulletins can be purchased online here. Longtime HMNH visitors might recognize the artwork on the covers of Bulletins 29 and 30.

All told, it painted a dynamic picture of the world between 300 and 250 million years ago, when the continents were coalescing into the supercontinent of Pangea, when the coal forests of the earlier Carboniferous period were losing ground to conifers and other plants more tolerant of drier climates, and when vertebrates began fine-tuning their adaptations to terrestrial life, diversifying into a riot of forms and leaving bones, footprints, and other traces in red rocks around the world.

Many of the illustrations shown in the HMNH’s Dispatch from the Permocarboniferous series were published in a symposium volume on “The Permian of Central New Mexico,” and all participants got a stylish, Permian Blue Bustin’ up Sphenacodonts T-shirt in honor of the occasion.

This weekend’s Albuquerque Tribune has a good article on the Symposium with additional background (and this illustration in the print version).

Farther inland, the moon climbs above a tropical forest of tree-sized horsetails and a different dance commences. Antennae probe the thick, humid air and the moonlight glints across multi-faceted eyes. Rivers of roughened cuticle eight feet long flow up from the frond litter and across the forest floor, and the air is filled with rustling as they snake around the gritty trunks of the horsetail jungle.

One by one, giant centipede-like forms emerge from the forest along the edge of an ancient lake. Their pace slows as they crawl across the lakeshore mud, but their stride never falters. Dozens of stout, spiny legs undulate in absolute precision, propelling the animals across the beach towards moonlit rendezvous. Their dance, unlike that of the horseshoe crabs, will falter after a few million years. The world will change, and their unparalleled invertebrate stature will prove impossible to maintain.

Year after year, the number of Arthropleura on the beach will diminish. None will remain at the close of the Carboniferous, but in certain places, the footsteps of their dance will be preserved.