Eric Shipton yeti snowprint revisited

So odd, so different,
it might just be real. It all started with a photograph by Eric Shipton from decades ago of a single large footprint in the snow of the Himalayan Mountains (Fig. 1). Here I simply added bones based on the apparent primate nature of the trackmaker and included gorilla pedal data for comparison.

Figure 1. Eric Shipton snowprint of Yeti with hypothetical bones and PILs applied. At top is pes of Gorilla. Ice pick for scale.

Figure 1. Eric Shipton snowprint of Yeti with hypothetical bones and PILs applied. At top is pes of Gorilla. Ice pick for scale. The impressions of digits 2 and 3 indicate logical interpretation with toe drag to avoid broken toe /#2 and nussubg toe #3 impression.

Distinct from human tracks,
the big toe of the Himalayan trackmaker is much bigger and does not extend as far as in humans. The tracks is wider than in humans. Digit 2 appears to be shorter than in humans.

Several years ago an expert of yeti and bigfoot, Dr. Jeff Meldrum,
appeared on ‘Joe Rogan Questions Everything’ #2 with Duncan Trussell (audio only, click to listen via YouTube). While Joe and Duncan tried to add levity to the discussion, Dr. Meldrum portrayed the facts as he knew them, keeping speculation to a minimum.

We touched on this subject
about a year ago earlier here.

Bipedal crocodylomorph (or giant pterosaur tracks?) from Korea

Kim et al. 2020 describe
sets of 18-24cm narrow-gauge tetradactyl (four-toed) bipedal tracks from the Early Cretaceous (Aptian?) coast of South Korea they name Batrachopus grandis (Figs. 1, 2) a new ichnospecies. The authors attribute the tracks to a large (3m) crocodylomorph. They also note: “Surprisingly, the trackways appear to represent bipedal progression which is atypical of all known smaller batrachopodid trackways.”

You might find their logic train interesting. (See below.)

By the way, such narrow-gauge tracks (Fig. 2) are also atypical for Cretaceous crocs and azhdarchid pterosaurs, like the Late Cretaceous trackmaker of the ichnospecies, Haenamichnus (Figs. 2, 3).

On the other hand, basalmost Triassic crocs were all narrow-gauge bipeds. None of these were large (but that can change), plantigrade (but that can change) or left tracks (that we know of).

Such narrow-gauge tracks were also typical for strictly bipedal pterosaurs, like the coeval (Early Cretaceous) Shenzhoupterus (Figs. 5–7), a taxon overlooked by Kim et al. 2018, 2020.

Figure 1. Batrachopodus grandis tracks from Kim et al. 2020. Note the digits are shorter than the metatarsals and the heel is half the maximum width of the foot, matching both Early Jurassic Protosuchus and coeval (Early Cretaceous) Shenzhoupterus.

Figure 2. Batrachopus tracks (2nd from left) compared to other croc tracks.

Figure 2. Batrachopodus tracks (2nd from left) compared to other croc tracks. Haenamichnus uhangriensis, azhdarchid quadrupedal pterosaur tracks shown at far right, with three fingered manus track, outside and slightly behind the oval (here at this scale) pedal track.

From the Kim et al. abstract:
“This interpretation helps solve previous confusion over interpretation of enigmatic tracks of bipeds from younger (? Albian) Haman formation sites by showing they are not pterosaurian as previously inferred. Rather, they support the strong consensus that pterosaurs were obligate quadrupeds, not bipeds.”

Consensus = current opinion. What you really want  and deserve is evidence! (…and not to overlook evidence that is already out there). Peters 2000, 2011 showed that many pterosaurs were bipedal. Specific beachcombing clades were quadrupedal secondarily.

Figure 2. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

Figure 3. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

Unfortunately,
basal crocodylomorph feet are almost entirely absent from the fossil record in tested taxa in the large reptile tree (LRT, 1697+ taxa). The only exception is bipedal and likely digitigrade, Terrestrisuchus (Fig. 4). We don’t get another complete set of toes for testing until quadrupedal and plantigrade Protosuchus (Fig. 4), a not so basal crocodylomorph, that had the slightly more gracile digit 4 common to all extant crocs. Digit 4 does not appear to be any more gracile than the other toes in the new South Korean tracks, but let’s overlook that trifle for the moment.

Figure 2. Same feet, reordered according to the large reptile tree. Only Terrestrisuchus and Protosuchus are croc-like archosaurs here. Poposaurs are basal dinosaurs.

Figure 4. Same feet, reordered according to the large reptile tree. Only Terrestrisuchus and Protosuchus are croc-like archosaurs here.

Perhaps that is why Kim et al. write:
“Lower Jurassic Batrachopus with foot lengths (FL) in the 2–8 cm range, and Cretaceous Crocodylopodus (FL up to ~9.0 cm) (Fig. 2) known only from Korea and Spain registered narrow gauge trackways indicating semi-terrestrial/terrestrial quadrupedal gaits. Both ichnogenera, from ichnofamily Batrachopodidae, have been attributed to Protosuchus-like semi-terrestrial crocodylomorphs.”

… with a wider-gauge quadrupedal track.

On that note: The type species for Batrachopus is much smaller, fleshy, quadrupedal, narrow-gauge, with pedal impressions just behind the much smaller manus impressions.

By the start of the Cretaceous all the earlier bipedal crocodylomorphs were extinct, according to the current fossil record. Shenzhoupterus, from China, was a nearby contemporary of the South Korean trackmaker with nearly identical feet and gait. Did I hear someone say, “Occam’s Razor“? Did someone mention, “taxon exclusion”?

Earlier Kim et al. 2012 described similar tracks
as pterosaurian. Back then they were matched here to a giant Shenzhoupterus (Figs. 5–7), a coeval (Aptian, Early Cretaceous) dsungaripterid relative found in nearby China, with forelimbs less likely to reach the ground. Later a partial skeleton of a giant Late Cretaceous pterosaur from France, Mistralazhdarcho (Vullo et al. 2018), was reidentified here as a giant shenzhoupterid, rather than an azhdarchid. So shenzhoupterids were not restricted in size.

Kim et al report on, “Distinguishing crocodilian from pterosaurian trackways.”
“An unexpected result of the discovery of B. grandis trackway has been to shed light on a the controversial issue of pterosaur locomotion debated since the 1980 and 1990s: were pterosaurs bipedal or quadrupedal?

The answer is some were bipedal. Others were quadrupedal (Peters 2000, 2011, not cited by Kim et al.). It all depends on the clade and their niche.

Kim et al continue:
“These debates, mainly concerning relatively small pterosaurian tracks, have largely been resolved in favor of quadrupedalism.

Largely? Does that mean Kim et al. recognize exceptions? If so, they were not cited. More importantly, look for any other distinguishing traits in what follows from the Kim et al. text.

Kim et al continue:
“However, some uncertainty remained regarding tracks of purported ‘giant’ pterosaurians that were described as ‘enigmatic’ and inferred to have progressed bipedally (Kim et al. 2012). These trackways from the Lower Cretaceous, Haman Formation, at the Gain-ri tracksite, Korea were named Haenamichnus gainensis and inferred to represent, large, plantigrade pterodactyloid pterosaurs that might have walked bipedally so that the long wings did not become mired in the substrate. It was further inferred they may have been wading in shallow water.”

amples from the Lower Cretaceous, Gain, Korea trackway

Figure 5. Samples from the Lower Cretaceous, Gain, Korea trackway (left) along with original tracings of photos, new color tracings of photos with hypothetical digits added in red, then candidate trackmakers from the monophyletic Shenzhoupterus/Tapejarid clade.

Estimating Gain pterosaur trackmakers from track sizes and matching taxa.

Figure 6. Estimating Gain pterosaur trackmakers from track sizes and matching taxa. Note the Shenzhoupterus manus is a wee bit too short to touch the substrate as in Tupuxuara and many other derived pterosaurs.

Figure 1. Mistralazhdarcho compared to reconstructions of Shenzhoupterus and Nemicolopterus.

Figure 7. Mistralazhdarcho compared to reconstructions of Shenzhoupterus and Nemicolopterus.

Kim et al continue:
“We can now confirm confidently, that these tracks from the Gain-ri tracksite and others from Adu Island: are identical to poorly preserved large Batrachopus trackways. Thus, they should be removed from Haenamichnus and regarded as large poorly preserved batrachopodid tracks. The type specimen then tech- nically becomes Batrachopus gainensis (comb nov.). Thus, H. gainensis becomes a footnote to ichnotaxonomic history, shown to be an extramorphological expressions large of Batrachopus, only recognizable retrospectively after comparison with B. grandis. Therefore ichnologists may retrospectively choose to regard H. gainensis as a nomen dubium, and find little value in the trival name (gainensis). Alternatively they may simply refer to the Haman Formation tracks as Batrachopus cf. grandis.

Taken on its face, this is a rare instance of a paleontologist admitting a mistake. The other option is: both tracks are pterosaurian. So far, as you’ll note, the authors have not pointed to any factors, other than ‘bipedalism’, that would dissuade a pterosaurian trackmaker interpretation. I will admit and you can see (Figs. 4–5) that the pedes of Protosuchus and Shenzoupterus are rather close matches when covered with pads.

Kim et al continue:
“Note that the Gain-ri and Adu island trackways are from the Haman Formation and so these occurrences indicate a widespread distribution in space (three sites) and time (two formations) of this distinctive apparently bipedal morphotype. The pes tracks from the two Haman Formation sites are also larger (27.5–39.0 cm long), but with trackway proportions (step, stride, pace angulation etc.,) quite similar to those from the Jinju Formation.”

“The identification of the Haman Formation trackways as poorly preserved large batrachopodid tracks apparently suggests that the trackmakers habitually progressed bipedally. Alternatively the same speculative arguments for apparent rather than real bipedalism would have to be invoked as was the case with the Jinju material. Moreover, in almost all cases the trackways are very narrow gauge with a narrower straddle than seen in modern crocodylians. It is also of interest that least five subparallel more or less equally spaced trackways were registered on the level 4 surface. This suggests either that the trackmakers may have been gregarious, or that they were following a physically controlled route, such as a shoreline, defined by the paleoenvironment.”

Still no distinguishing traits, other than bipedalism, according to the authors. And note, they never considered the coeval and neighboring pterosaur, Shenzhoupterus, which is also a close match for the new tracks. They chose to invent a croc trackmaker rather than consider a pterosaurian trackmaker, evidently bowing to the consensus (their word, not mine, see above) and to follow Dr. Bennett’s curse and keep their blinders on. I wish they had dived deeper into the literature and evidence instead of following the crowd.


References
Hwang KG, Huh M, Lockley MG, Unwin DM and Wright JL 2002. New pterosaur tracks (Pteraichnidae) from the Late Cretaceous Uhangri Formation, southwestern Korea. Geology Magazine 139(4): 421-435.
Kim, JY et al. 2012. Enigmatic giant pterosaur tracks, and associated ichnofauna from the Cretaceous of Korea: implications for bipedal locomotion of pterosaurs. Ichnos 19, 50–65 (2012).
Kim KS, Lockley MG, Lim JD, Bae SM and Romilio A 2020. Trackway evidence for large bipedal crocodylomorphs from the Cretaceous of Korea. Nature Scientific Reports 10:8680 | https://doi.org/10.1038/s41598-020-66008-7
Lockley, MG et al. 2020. First reports of Crocodylopodus from Asia: implications for the paleoecology of the Lower Cretaceous.Cretaceous Research (2020) (online, March 2020).
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos, 7: 11-41
Peters D 2011.
A Catalog of Pterosaur Pedes for Trackmaker Identification Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605
Vullo R, Garcia G, Godefroit P, Cincotta A, and Valentin X 2018.
 Mistralazhdarcho maggii, gen. et sp. nov., a new azhdarchid pterosaur from the Upper Cretaceous of southeastern France. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1502670.

https://pterosaurheresies.wordpress.com/2012/03/25/giant-bipedal-pterosaur-tracks-from-korea/

https://pterosaurheresies.wordpress.com/2018/10/19/mistralazhdarcho-a-new-pterosaur-but-not-an-azhdarchid/

Crayssac basal pterosaur tracks? …or tenrec tracks?

Earlier we looked at Mazin and Pouech 2020
who claimed they had discovered “the first non-pterodactyloid pterosaurian trackways.” At the time, only the abstract was available to discuss and criticize.

Nine years ago
Peters 2011 published anurognathid tracks, which makes them the first non-pterodactyloid pterosaurian trackways published. Notable by its exclusion, Mazin and Pouech 2020 did not cite, “A catalog of pterosaur pedes for trackmaker identification” (Peters 2011), confirming Dr. S. Christopher Bennett’s threat, You will not be published. And if you are published, you will not be cited.”

Now that I have seen the paper and the tracks,
(Figs. 1, 2) let’s determine what sort of tetrapod made those tracks named, Rhamphichnus crayssacensis, because they don’t look like other pterosaur tracks, as workers (see below) acknowledge.

Diagnosis from Mazin and Pouech 2020:
“Quadrupedal trackway with tridactyl digitigrade manus-prints and pentadactyl plantigrade to digitigrade pes-prints. Subparallel manus digit-prints orientated anteriorly. Pentadactyl pes-prints with more or less divergent digit prints. Pedal digit V divergent and postero-laterally rejected. Manus trackway slightly to clearly wider than the pes trackway.”

Distinct from typical pterosaur manus tracks:

  1. tridactyl digit prints are subparallel (rather than widely splayed)
  2. digits are oriented anteriorly (rather than laterally to posteriorly)
  3. digits sometimes include additional medial and lateral impressions (never seen in other pterosaur tracks)
  4. no claw marks are present (that seems wrong based on Fig. 1)
  5. the manus impression is just anterior to the pes impression (rather than laterally and posteriorly, as in other pterosaur tracks)
Figure 1. Images from Mazin and Pouech 2020. Some manus tracks have at least four digits.

Figure 1. Images from Mazin and Pouech 2020. Some manus tracks have at least four digits.

There are many
basal and derived pterosaurs with pedal digit 2 (or 2 and 3) the longest, distinct from Triassic pterosaurs. These were all examined and rejected as potential trackmakers matching Rhamphichnus for various reasons.

I also looked at 1600+ non-pterosaur trackmakers
due to the many unexpected traits (see list above) present in the Rhamphichnus tracks.

First and foremost,
the pterosaur antebrachium (radius + ulna) could not be pronated to produce anteriorly-oriented Rhamphichnus tracks. Due to folding and flying issues, pterosaurs, like birds, do not have the ability to pronate and supinate the wing. That’s why all pterosaur manus tracks are oriented laterally with fingers at full extension, impressing into the substrate. That manus digit 3 is often rotated posteriorly is a clue to its lepidosaurian ancestry. These facts form the hypothesis of a secondarily quadrupedal configuration for some, but not all pterosaurs.

One overlooked trackmaker stood out as a good match
for Rhamphichnus: the tenrec, Tenrec (Fig. 2), a small digitigrade quadrupedal mammal currently restricted to Madagascar. The medial and lateral manual digits are shorter than 2-4, which are parallel in orientation.

Figure 2. Rhamphichnus tracks compared to a Tenrec trackmaker.

Figure 2. Rhamphichnus tracks compared to a Tenrec trackmaker. The brevity of pedal digit 5 is a mismatch, but a related taxon, Leptictidium, likewise reduces pedal digit 5.

One of those Tenrec sisters,
Rhynchocyon, greatly reduces manual digits 1 and 5, but pedal digit 3 is the longest.

Another Tenrec sister,
Leptictidium (Fig. 3), has a pes with a reduced pedal digit 5, but a short digit 2, but the manus is also a good match for Rhamphichnus. So there is great variation in the pes of tenrec clade members. Still, a small tenrec-like mammal remains a more parsimonious trackmaker than any Late Jurassic pterosaur. They were able to pronate the manus!

Figure 2. Elements of Leptictidium from Storch and Lister 1985.

Figure 3. Elements of Leptictidium from Storch and Lister 1985.

Due to taxon exclusion,
Mazin and Pouech 2020 did not consider alternative trackmakers for the pterosaur-beach Rhamphichnus tracks that don’t match other pterosaur tracks or extremities. Now we’re stuck with an inappropriate name for these Late Jurassic tenrec tracks.

A late Jurassic tenrec?
The large reptile tree (LRT, 1637 taxa) supports the probability that a sister to Tenrec was present in in the Late Jurassic based on the coeval presence of derived members of Glires (Multiturberculata). Placental mammal fossils remain extremely rare in the Mesozoic, but these impressions add to their chronology.

It is worth repeating, due to the subject matter,
the Crayssac pterosaur beach still includes the pes of the JME-SOS 4009 specimen attributed to Rhamphorhynchus, as mentioned earlier. Here it is again (Fig. 4).

Pes of Rhamphorhynchus and matching track

Figure 4. Crayssac track different from all others. Inset: Pes of Rhamphorhynchus muensteri JME-SOS 4009, no. 62 in the Wellnhofer catalog

twitter.com/Mark Witton mistakenly reports:
“Turns out we’ve been over-thinking it (pedal digit 5): it just lays flat on the ground during walking, like a regular toe.”

“For one, the walking fingers face forward, not sideways, as in pterodactyloids. This seems weird, but it turns out that non-ptero wing fingers fold roughly perpendicular to the walking digits.”

These basic bungles by a PhD pterosaur worker
demonstrate the dominance of myth-making among purported experts due to accepting published results like a journalist, without testing them, like a scientist. Dr. Witton’s 2013 pterosaur book is full of similar mistakes reviewed here in a seven-part series.


References
Mazin J-M and Pouech J 2020.The first non-pterodactyloid pterosaurian trackways and the terrestrial ability of non-pterodactyloid pterosaurs. Geobios 16 January 2020. PDF
Peters, D. 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification
Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605

https://pterosaurheresies.wordpress.com/2020/01/18/first-non-pterodactyloid-pterosaurian-trackways-ever-described-no/

 

New yeti tracks?

Photos from Mountaineers in the Indian Army
show several long (32″) prints in the snow, one directly in front of the other. The New York Times covered the story (see citation below).

Figure 1. 2019 yeti tracks found in Nepal and posted online.

Figure 1. 2019 yeti tracks found in Nepal and posted online. That’s an ice pick alongside for scale. Is this a combo track? See text.

These are definitely not bear tracks.
The large digit 1 tells us they were made by a primate… if this is a single impression.

The only question is…
did the primate use its own feet to make foot tracks, or was it wearing yeti shoes? Or is this a combination track?

Unfortunately
only one footprint is shown. It would have been more useful to see a complete set, to see if there was a right foot also, and what variation there might be as the trackmaker navigated the terrain, its own weight shifts, etc.

It’s a nice first step.
To its credit, the trackmaker had parallel interphalangeal lines (PILs). Cheap knock-offs and fakes generally overlook this detail. The NY Times.com story suggests it is a combination track from a mama bear and her cub. We should consider all possibilities.


References
NY Times.com story

Not even an elevated Dimetrodon made these Dimetropus tracks

Matching tracks to trackmakers
can only ever be a semi-rewarding experience. Estimates and exclusions can be advanced. Exact matches are harder to come by. This is due to both the vagaries and varieties of sequential footprints in mud or sand, and to the rarity of having skeletal data that matches.

Figure 1. Dimetrodon adult, juvenile, skull, manus, pes.

Figure 1. Dimetrodon adult, juvenile, skull, manus, pes. Note the asymmetry of the fingers and toes. Dimetropus tracks were named for this taxon.

Which brings us to Dimetropus
Traditionally Early Permian Dimetropus tracks (Fig. 2–8; Romer and Price 1940) have been matched to the coeval pelycosaur, Dimetrodon (Fig. 1)—but only by narrowing the gauge of the Dimetrodon feet and elevating the belly off the surface, as Hunt and Lucas 1998 showed.

Today we’ll take a look at some other solutions
not involving Dimetrodon doing high-rise pushups. Several distinctly different tracks have fallen into the Dimetropus wastebasket. Let’s look at three ichnospecimens.

Traditionally, and according to Wikipedia,
citing Hunt and Lucas 1998: “Trackways called Dimetropus (“Dimetrodon foot”) that match the foot configuration of large sphenacodontids show animals walking with their limbs brought under the body for a narrow, semi-erect gait without tail or belly drag marks. Such clear evidence for a more efficient upright posture suggests that important details about the anatomy and locomotion of Sphenacodon and Dimetrodon may not be fully understood.” Hunt and Lucas blamed traditional reconstructions of Dimetrodon for the mismatch. Instead they should have looked at other candidate trackmakers from the Early Permian. Note the asymmetric manus and pes of Dimetrodon (Fig. 1). Those don’t match the tracks no matter how high the belly is above the substrate. Dimetrodon is just fine the way it is.

Figure 1. Early Permian Dimetropus tracks matched to Middle Triassic Sclerosaurus, one of the few turtle-lineage pareiasaurs for which hands and feet are known.

Figure 2. Early Permian Dimetropus tracks matched to Middle Triassic Sclerosaurus, one of the few turtle-lineage pareiasaurs for which hands and feet are known.

A better match
can be made to the Middle Triassic pre-softshell turtle pareiasaur, Sclerosaurus (Fig. 2). Note the symmetric manus and pes like those of living turtles (Fig. 3) and the Dimetropus specimen in figure 2.

Figure 2. Snapping turtle tracks in mud. Note the relatively narrow gauge and symmetric imprints.

Figure 3. Snapping turtle tracks in mud. Note the relatively narrow gauge and symmetric imprints like those of Dimetropus.

Living turtle tracks
like those of the snapping turtle, Macrochelys (Fig. 3) are also symmetrical and surprisingly narrow gauge. Let’s not forget, Dimetropus tracks occur in Early Permian sediments, predating the earliest fossil turtles, like Proganochelys, first appearing in the Late Triassic. Let’s also not forget, in the large reptile tree (LRT, subset Fig. 7) Proganochelys is not the most basal turtle and valid predecessors (not eunotosaurs) had similar hands and feet.

FIgure 4. Dimetropus tracks compared to a large Dimetrodon matched to finger and toe tips. Hand too wide. Compared to a small Dimetrodon. Hand too small. Compared to a normal size Hipposaurus, good match even if not all the digits are known.

FIgure 4. Dimetropus tracks compared to a large Dimetrodon matched to finger and toe tips. Hand too wide. Compared to a small Dimetrodon. Hand too small. Compared to a normal size Hipposaurus, good match even if not all the digits are known.

A second set of Dimetropus tracks
(Fig. 4, right), have distinctive heels behind symmetric + asymmetric imprints. A large Dimetrodon could not have made these tracks because they are too narrow. A small Dimetrodon had extremities that were too small, as the animated GIF shows.

FIgure 3. Hipposaurus compared Dimetropus. The overall and leg length is right, as are many of the digits. Unfortunately the medial digits are too short in Hipposaurus. Hipposaurus has a narrower gauge and lifted its belly of the ground, as did the Dimetropus trackmaker.

FIgure 5. Hipposaurus compared Dimetropus. The overall and leg length is right, as are many of the digits. Unfortunately the medial digits are too short in Hipposaurus. Hipposaurus has a narrower gauge and lifted its belly of the ground, as did the Dimetropus trackmaker.

Fortunately,
we also have Middle Permian basal therapsid, Hipposaurus (Figs. 4, 5), a close relative of the last common ancestor of all pelycosaurs (see Haptodus and Pantelosaurus; Fig. 6). No doubt Hipposaurus elevated its torso on a narrow gauge track, with manus tracks slightly wider than pedal traces, as in Dimetropus. Both the carpus and tarsus are elongate, matching Dimetropus tracks.

Unfortunately,
we don’t have all the phalanges for the Hipposaurus manus and pes (Fig. 4). Drag marks can lengthen a digit trace. Flexing a claw into the substrate can shorten a digit trace. It is also important to note that during the last moment of the manus propulsion phase, the medial and lateral metacarpals can rotate axially, creating the impression of an ‘opposable thumb’ in the substrate. Note that no two ichnites are identical, despite being made one after another by the same animal.

Figure 5. Closeup of Hipposaurus manus and pes compared to random Dimetropus manus and pes tracks. Note, some digits remain unknown. Some digits might create drag marks. Others may dig in a claw or two apparently shortening the digit imprint.

Figure 6. Closeup of Hipposaurus manus and pes compared to random Dimetropus manus and pes tracks. Note, some digits remain unknown. Some digits might create drag marks. Others may dig in a claw or two apparently shortening the digit imprint.

At present
a more primitive sister to Hipposaurus is the best match for the Hunt et al. 1995 Dimetropus tracks and the Early Permian timing is right.

FIgure 6. Subset of the LRT focusing on Hipposaurus and its relatives, color coded to time.

FIgure 7. Subset of the LRT focusing on Hipposaurus and its relatives, color coded to time. Hipposaurus is nearly Early Permian and probably had its genesis in the Early Permian.

In the popular press
NewScientist.com reported, “We’ve drawn iconic sail-wearing Dimetrodon wrong for 100 years. Some palaeontologists did offer an explanation – that Dimetrodon thrashed its spine from side to side so much as it walked that it could leave narrow sets of footprints despite having sprawled legs.” That hypothesis, based on omitting pertinent taxa, is no longer necessary or valid.

Abbott, Sues and Lockwood 2017 reported the limbs of Dimetrodon were morphologically closest to those of the extant Caiman, which sits on its belly, but also rises when it walks.

It is unfortunate that no prior workers considered Hipposaurus, a nearly coeval taxon with Dimetropus having matching slender digits, long legs, an erect carriage, and just about the right digit proportions.

A third ichnotaxon,
Dimetropus osageorum (Sacchi et al. 2014), was considered a possible caseid, rather than a sphenacodontid, but caseids have more asymmetric digits (= a shorter digit 2). Unfortunately, taxon exclusion also hampered the Sacchi et al. study. They did not consider Early Permian stephanospondylids, Late Permian pareiasaurs in the turtle lineage and Triassic turtles. No skeletal taxon is a perfect match for this ichnotaxon, but the Late Cretaceous turtle, Mongolochelys, is close  (Fig. 8). It took some 200 million years after the trackmaker of Dimetropus for the lateral pedal digits to shrink, but everything else is a pretty good match.

Figure 7. Dimetropus oageorum from Sacchi et al. 2014 matched to Mongolochelys, a Late Cretaceous turtle. Only pareiasaurs and turtles, among basal taxa, have such a long manual and pedal digit 2.

Figure 8. Dimetropus oageorum from Sacchi et al. 2014 matched to Mongolochelys, a Late Cretaceous turtle. Only pareiasaurs and turtles, among basal taxa, have such a long manual and pedal digit 2. The reduction of pedal digits 4 and 5 are derived in this late surviving basal turtle.

Also compare the hands and feet
of Early Permian Dimetropus osageorum (Fig. 8) to the Middle Triassic Sclerosaurus (Fig. 2). Dimetropus is solid evidence that turtle-ancestor pareiasaurs were present in the Early Permian (see Stephanospondylus, an Early Permian turtle and pareiasaur ancestor).

Saachi et al. conclude, “At the same time, the process of attributing ichnotaxa, on the basis of well preserved tracks and by comparison with known skeletal remains, is validated.”  True. Unfortunately all prior workers overlooked a wider gamut of skeletal taxa to compare with their ichnotaxon in their search for a ‘best match.’ Perhaps they felt restricted by time (Early Permian). As the above notes demonstrate, that is not a good excuse.

References
Abbott CP, Sues H-D and Lockwood R 2017. The Dimetrodon dilemma: reassessing posture in sphenacodonts. GSA annual meeting in Seattle, WA USA 2017. DOI: 10.1130/abs/2017AM-307190
Hunt AP and Lucas SG 1998. Vertebrate tracks and the myth of the belly-dragging, tail-dragging tetrapods of the Late Paleozoic. Bulletin New Mexico Museum of Natural History and Science. 271: 67–69.
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605
Romano M, Citton P and Nicosia U 2015. Corroborating trackmaker identification through footprint functional analysis: the case study of Ichniotherium and Dimetropus. Lethaia https://doi.org/10.1111/let.12136
Romer AS and Price LI 1940. Review of the Pelycosauria: Geological Society of America, Special Paper 28:538pp
Sacchi E, Cifelli R, Citton P, Nicosia U and Romano M 2014. Dimetropus osageorum n. isp. from the Early Permian of Oklahoma (USA): A trace and its trackmaker. Ichnos 21(3):175–192. https://doi.org/10.1080/10420940.2014.933070

Earlier than they thought…

Figure 1. The Middle Devonian tetrapod tracks from 395 mya are 35 million years older than Ichthyostega, which could not walk like this on land.

Figure 1. The Middle Devonian tetrapod tracks from 395 mya are 30 million years older than Ichthyostega, which could not walk like this on land.

The discovery of early Middle Devonian (395 mya) tetrapod tracks (elevated belly and not dragging a tail, Fig. 1) prompts today’s post. More on this discovery online here and below.

New discoveries keep pushing prior time envelopes in palaeontology. In this case, these tracks predate Ichthyostega and kin by 30 million years. They also provide at least 55 million years for evolution to produce the first amniotes in the Viséan, 340 mya. At that time amniotes (reptiles) were already a diverse clade including Eldeceeon, Westlothiana and Casineria. That means the very first amniotes might have been contemporaries of Ichthyostega 25 million years earlier at 365 mya…or even earlier if those tracks at 395 mya are considered. Those numbers appear to break all the current paradigms.

So much so that I wonder about the validity of the strata dating.
Niedźwiedzki et al. 2010 reported the dates were secure. Even so, they are unexpected, to say the least (Fig. 2). Added later on pub day: This year (Narkiewicz and Narkiewicz 2015), the age of the Zachełmie Quarry sediment (determined by conondonts) was modified only slightly (4-5 my younger).

On a similar note
Bird tracks purported to be created in Triassic sediments were later identified as Eocene sediments. So such mistakes do happen. It’s a hard call…

Figure 2. The Devonian and events within it. Here the new tetrapod trackways from 395 mya is the lower blue bar.

Figure 2. The Devonian and events within it. Here the new tetrapod trackways from 395 mya is the lower blue bar.

Other time bumps
Earlier we looked at an erroneous (way too late) estimate for the origin and radiation of burrowing skinks (amphisbaenids). The traditional date for the origin of lizards (Wiki reports: Middle Jurassic) also fails to take into account Lacertulus (Late Permian) and Ascendonanus (early Permian).

Earlier the origin of snakes was pushed back several millions years.

Turtles had their origins long before the late Triassic, where their earliest known and already diverse fossils are found. Stephanospondylus lived during the Early Permian. We don’t know if it lived alongside turtles of more modern aspect (perhaps, though still retaining teeth) or shortly preceded them. From what we know about turtles, they don’t do anything quickly.

The persistence of basal taxa into the Cretaceous or to the present should come as no surprise when Sphenodon, the extant sphenodontid, is considered.

To make matters worse,
as you already know, the first appearance of any fossil or ichnite in rocks probably does not the first appearance of the morphotype, but instead probably represents the height of that form’s  radiation — by which time other undiscovered forms had also probably radiated.

On the other hand…
The origin of some groups, like pterosaurs, hominids, whales, bats, birds and dinosaurs appear to be more tightly constrained, based on more extensive fossil records.

References
Niedźwiedzki G, Szrek P,  Narkiewicz K, Narkiewicz M and Ahlberg PE 2010. Tetrapod trackways from the early Middle Devonian period of Poland. Nature 463, 43-48. doi:10.1038/nature08623
Narkiewicz, K and Narkiewicz, M 2015, The age of the oldest tetrapod tracks from Zachełmie, Poland. Lethaia, 48: 10–12. doi: 10.1111/let.12083

http://onlinelibrary.wiley.com/enhanced/doi/10.1111/let.12083