Véra Eisenmann

Natural Trap, Wyoming, Introduction

2013-10-19T10:31:38Z

It was John Howe who studied the equids of Natural Trap but his manuscript was never published.

Instead, part of his work was included in "Eisenmann V., Howe J., Pichardo M. 2008 (published in 2011) : Old World Hemiones and New World slender species (Mammalia, Equidae). Palaeovertebrata 36(1-4) : 159-233, 73 fig., 4 append. fig., 8 tabl.".

This web article is based on the data he kindly communicated to me.

The details of the data and their elaboration may be found in the Appendix Natural Trap, Appendix.
The doubtful measurements are printed in red and highlighted in yellow ; if "corrected" they appear in blue and are highlighted in blue.

In many cases the referral to a particular species is difficult or impossible, partly because of the material itself, partly because of the measurements chosen by John Howe and his students.

The size range is very large. Although the equid fossils are extremely numerous, all size groups are not equally represented. I believe that are present :
– a large Amerhippus : cranium,teeeth, bones Natural Trap, Large Amerhippus
– an Amerhippus conversidens : cranium, mandibles, bones Natural Trap Amerhippus conversidens
– an Amerhippus cf. pseudaltidens : mandible, teeeth, bones Natural Trap Amerhippus cf pseudaltidens
– an Equus caballus : mandibles, teeth, bones Natural Trap, Caballine

Natural Trap, Tibiae, Data

2013-10-18T21:14:58Z

In Table 1 are the original data (2 sheets) provided by John Howe. Some measurements seemed aberrant ; the are printed in red and highlighted in yellow ; the same specimen was measured twice and only the mean (X) was used. In Table 2 the corrected data I used are printed and highlighted in blue ; later on I discarded the diaphysis diameter because of its too large variation.

Scatter diagrams (Fig.1-3) show one distal end exceedingly large (36640), one specimen exceedingly robust (52070), and three very large specimens (33253, 47808, and 54449) ; a large variation exists even among the other tibiae. Most Natural Trap tibiae are bigger than in extant E. hemionus onager.

Natural Trap, Crania and Mandibles, Data

2013-10-18T21:00:39Z

- Natural Trap, Appendix

Natural Trap, Ph3, Data

2013-10-18T20:23:29Z

John Howe sent me copies of his data on seven sheets. Some data were redundant. In Table 1 you may find the original data and in Table 2 - the ones I have used.
A few phalanges were obviously different from the rest by their size. They will be discussed later, after the bulk of the material (ca. 125 middle-sized specimens).

In Fig.1, all Natural Trap Ph3 are compared to all extant Hemiones and Kiangs.

Sorting the anterior Ph3 from the posterior
I'll discuss elsewhere the general problem of this kind of sorting. For the moment I'll only say that, unfortunately, two important measurements were not taken : plantar length and plantar circumference. Thus, I tried to sort the Ph3 according to the proportions of the articular surface : in the same individual, the articular width of the anterior Ph3 is larger, but naturally when many individuals are mixed the sorting is uncerain : Fig.2 (all Hemiones and Kiangs), Fig.3 (midle-sized Natural Trap).

Conclusions
Fig.4 compares the middle-sized and the small specimens of Natural Trap to all E. hemionus and E. kiang Ph3. I cannot go farther than saying that they are about the same size.

Fig.5 compares the large specimens of Natural Trap to E. przewalskii Ph3. Fig.6 compares the same to A. occidentalis Ph3.

The specimen 50821 could be a posterior Ph3 of a Caballine or an anterior of A. occidentalis. Others could belong to a very large A. occidentalis (Fig.6).

Natural Trap, Ph2, Data

2013-10-18T18:12:56Z

Like for the first phalanges, I received from John Howe copies of his data on second phalanges (Ph2) on separated (10) sheets. A few data were redundant, in that cases I used their mean noted '-X'. In Table 1, you may find the original data, in Table 2 - the ones I used, and in Table 3 - the same after sorting the anterior Ph2 from the posterior.

Uusually a scatter diagram of distal articular width (6) versus maximal length (1) separates easily the anterior Ph2 (shorter and wider) from the posterior. In this case, I used the sum of minimal width (3) and distal articular width (6) versus maximal length (Fig.1).

This scatter diagram shows a bulk of slender Ph2 with little overlap and one uncertain specimen. Besides, a few phalanges seem rather large ; three rather small.
The remaining specimens are too large and/or too robust to belong with the precedent group.

Middle-sized slender Ph2 (A. cf. pseudaltidens)
Statistics (Table 4) on 87 supposed anterior Ph2 are compatible with a single form. Size and shape are similar to extant E. hemionus onager apart a smaller proximal depth (5). The corresponding bone by bone Simpson's diagram is in Fig.2.

Statistics on supposed 80 posterior Ph2 are also compatible with a single form, not very different from the extant E. hemious onager (Table 5). The corresponding bone by bone Simpson's diagram is in Fig.3.

Large slender Ph2
There are eight of them (Fig.4). I suppose that they come from a different level of Natural Trap.

Small slender Ph2
I do not know what to make of these three small specimens (Fig.5). The posterior, extremely slender, may be a juvenile ?

Caballine Ph2
Five anterior and seven posterior are close in size and proportions (Fig.6). to extant E. przewalskii or Mongolian horses Ph2.

A. leoni-like Ph2
I refer to A. conversidens two anterior Ph2. Although I have no data on A. leoni Ph2, this is a logical assumption in the context of other fossils of Natural Trap. One Ph2 of an extant E. africanus is smaller but otherwise not very different (Fig.7).

Natural Trap, Ph1, Data

2013-10-18T17:48:27Z

Like the rest of the material of Natural Trap, the first phalanges (Ph1) were measured by John Howe and his student(s). John Howe sent me copies of these data on nine sheets. Some data appeared redundant, either because they originated from the right and left side of the same animal or because the same specimen was measured twice by the same researcher or by two different ones. In Table 1 you may find the original data and in Table 2 - the ones I have decided to use.

One measurement (6 : supra-articular distal width) useful for distinguishing anterior from posterior phalanges was missing, and three other were at times inconsistent (7 : length of trigonum phalangis ; 10 : supra-tuberosital length and 13 : infra-tuberosital length) ; they were not used for the sorting.

A few phalanges were obviously different from the rest by their slenderness and/or their size (Fig.0). They will be discussed later. But the bulk of the material (ca. 130 slender middle-sized specimens) took me several weeks to sort out as anterior or posterior, and I am not even absolutely certain of the result.

Middle-sized slender Ph1 (A. cf. pseudaltidens)
In extant Hemiones, the anterior phalanges are almost always longer than the posterior, and the posterior are relatively broader and deeper. Although the slender Ph1 of Natural Trap do not belong to Hemiones, I tried to sort them out according to these criteria.

First I drew a scatter diagram of width at the middle of diaphysyis (3) versus maximal length (1). There appeared a kind of separation at between 81mm and 83mm of length. I decided to keep in mind that phalanges longer than 82.5 were probably anterior and those shorter than 81.5 - posterior, leaving a doubtful zone between 81 and 83 (Fig.1). This diagram evidenced the existence of five 'aberrant' specimens. It showed also that the width 3 was roughly the same in both groups.

I decided to attempt an 'unorthodox' approach by plotting the maximal lengtth versus the slenderness (Fig.2). Three of the five previous aberrant Ph1 were still present ; in addition two 'anterior' Ph1 plotted with the posterior, one well inside and the other in what could be considered as an 'overlap' zone.

The next step was to find the best way to use other data i.e the proximal and distal widths (4 and 14) and the proximal depth (5). The conventional scatter diagrams were not very helpful and I resorted again to unorthodox ones (Fig.3-6).

Eventually I decided to consider 67 Ph1 as anterior, and 65 as posterior. The Simpson's diagrams in Tables 3 and 4 show why I could not use the measurements 7 and 13 to sort the Ph1 into anterior and posterior. In accordance, they do not appear on the individual Simpson's diagrams in Fig.7 and 8. Simpson's diagrams of indet and problematic Ph1 are given in Fig.9. Unfortunately, I was unable to find any data of similar Ph1 apart a few specimens from Hay Springs measured by John Howe (Fig.11).

Large slender Ph1
There are only four of them (Fig.10). I am not certain that they are all anterior nor that they belong to a species different from the previous. There again I have no match except one Ph1 from E. semiplicatus of Hay Springs (Fig.11).

Very large anterior Ph1
It is strikingly similar to A. occidentalis anterior Ph1 from Rancho La Brea (Fig.12).

Caballine Ph1
Six anterior and five posterior are close in size and proportions to extant horses' phalanges (Fig.13). One is Icelandic horse, the other Mongolian.

A. leoni-like Ph1
I refer to A. conversidens five anterior Ph1 and four posterior (Fig.14-15). I found the data for comparison in Dalquest 1967 (Conkling and Slaton) while Arthur Harris kindly communicated his data on Dry Cave.

HARRIS A.H. & PORTER L.S.W. 1980. Late Pleistocene Horses of Dry Cave, Eddy County, New Mexico. Journal of Mammalogy 61(1) : 46-65.

Natural Trap, MT, Data

2013-10-18T16:49:46Z

Like the MC of Natural Trap, the third metatarsals (MT) were measured by John Howe (sheets I and II) and one student (sheets III and IV). The diagrams (Fig.1,2) show again that they did not measure the diaphysis depth (4) in the same way. There is no way to increase the measure 4 but there is a way to make in smaller : by measuring it just above the distal articulation, as was proposed by A. von den Driesch (1976). I assume that John Howe used this way. In Table 1 are the original data and in Table 2 - the ones I have decided to use after discarding the diaphysis depth measured by John Howe and suppressing some redundant data.

The scatter diagram of proximal width versus maximal length (Fig.3) shows that some MT are different from the rest by their slenderness and/or their size. They will be discussed later. The bulk of the material has hemione-like slenderness but the size is larger.

Middle-sized slender MT (A. cf. pseudaltidens)
Statistics and Simpson's diagrams bone by bone are in Table 3.

Large slender MT
Two specimens that may belng to the same animal (Fig.4).

A. leoni-like MT
I refer to A. cf. conversidens three MT (Fig.5). The Slaton Quarry data were published by Dalquest & Hugues (1965) and Dalquest (1967).

References

DALQUEST, W.W. & HUGHES, J.T., 1965.- The Pleistocene Horse Equus conversidens. The American Naturalist. Notes and discussions : 241-244.

DALQUEST, W.W., 1967.- Mammalls of the Pleistocene Slaton Local fauna of Texas. The Southwestern Naturalist, 12 : 1-30.

DRIESCH A. von den, 1976. - A guide to the measurement of animal bones from Archaeological sites. Peabody Museum Bulletins, Harvard University (1), 137p., 62 fig.

Natural Trap, MC, Data

2013-10-18T16:34:48Z

Like the rest of the material of Natural Trap, the third metacarpals (MC) were measured by John Howe (sheets I and II) and one student (sheets III and IV). Looking at the diagrams (Fig.1,2) it is obvious that they did not measure the diaphysis depth (4) in the same way. There is no way to increase the measure 4 but there is a way to make in smaller : by measuring it just above the distal articulation, as was proposed by A. von den Driesch (1976). I assume that John Howe used this way. In Table 1 are the original data and in Table 2 - the ones I have decided to use after discarding the diaphysis depth measured by John Howe and suppressing some redundant data.

The scatter diagram of diaphysis width versus maximal length (Fig.3) shows that some MC are different from the rest by their slenderness and/or their size. They are discussed in the main text. The bulk of the material has hemione-like slenderness but the size is larger.

Middle-sized slender MC (A. cf. pseudaltidens)
Statistics and Simpson's diagrams bone by bone are in Table 3.

Very slender MC
They seem close to the specimen from G Quarry (Fig.4).

A. leoni-like MC
I refer to A. cf. conversidens seven MC (Fig.5). The Bagget Ranch data were published by Quinn (1957).

Undetermined MC
Fig.6.

References

DRIESCH A. von den, 1976. - A guide to the measurement of animal bones from Archaeological sites. Peabody Museum Bulletins, Harvard University (1), 137p., 62 fig.

QUINN J. H., 1957. Pleistocene Equidae of Texas. Bureau of Economic Geology, University of Texas, Report of Investigations 33 : 51pp.

Natural Trap, Humeri, Data

2013-10-18T16:13:21Z

In Table 1, are the original data provided by John Howe (2 sheets).
Scatter diagrams (Fig.1 and 2) show that Natural Trap humeri are longer than in extant E. hemionus onager (Fig.1) as well as wider and flatter (Fig.2).
As in other limb bones, a few specimens seem larger, possibly because they come from another level of Natural Trap. One is shorter (nÂ° 51884) but not otherwise different.
Statistics of the main, gracile, group are in Table 2 ; Simpson's diagrams, bone by bone, in Fig.3.

- Natural Trap, Appendix

Natural Trap, Femora, Data

2013-10-18T15:58:55Z

In Table 1 are the original data (2 sheets) provided by John Howe. One specimen was measured twice ; two seem to be the left and right of the same animal. In Table 2 are the data I used (diaphysis and proximal depths were not used because they are difficult to measure and bring little information) ; later on I discarded also the diameter of caput femoris because of its too large variation.

Scatter diagrams (Fig.1-2) show three very large and robust specimens ; a large variation exists even among the other femora. Most Natural Trap femora are bigger than in extant E. hemionus onager.

Robust Femora (Fig.3)
– The largest one is similar to the average Amerhippus leoni.
– Two smaller may belong to a Caballine.

Gracile and very gracile Femora (Fig.4)
I am unable to propose any attribution for these specimens.