EDENTATA
The scarcity of edentates in the Deseado beds is in striking contrast
to their abundance in the Santa Cruz formation. Whereas in this latter
horizon over half of the finds are edentates, in the Deseado only eight
per cent. of the total collection belong to this group, and this is
doubtless a larger proportion than these animals represented in the
fauna; for the hundreds of small plates in a carapace, when scattered
greatly, increase the chance that some part of an individual will be
found, and most of the eight per cent. of finds are single plates. Most
of the plates found represent armadilloes, our collection containing
but one plate of a glyptodont, and no gravigrades. Ameghino’s
collections present about the same relations, but in the repeated trips
he found a few more traces of glyptodons and a very few gravigrades.
This scarcity of edentates can not be taken to mean that they were not
developed, for they are a peculiarly South American group, and as they
were developing somewhere into their great complexity, I take it to
mean that the climatic conditions were unfavorable in this particular
section.
As noted above, all previous finds have been isolated plates. We were
fortunate enough to find one specimen consisting of a carapace with ten
rows of movable plates in place, and parts of four rows of the pelvic
buckler together with over fifty isolated plates. A second specimen had
some fifty associated plates which were mostly from the pelvic buckler.
Dasypoda
The representatives of this group are so poorly known in the Deseado
beds that Ameghino has, in general, used the generic names of the Santa
Cruz for their description, and, so far as known, they are little
differentiated from those genera. There is as yet no material which
shows the association of skeletal parts with the carapaces. Therefore,
in this paper, comparisons are made wholly on the carapace, with the
expectation that the skeleton, when found, will correspond.
The Deseado species are but little less specialized than the Santa
Cruz, the carapace consisting of movable overlapping bands of plates
both in the anterior and body portions, while over the pelvic region
the plates are fixed, do not overlap, and form a pelvic buckler.
Ameghino has described a considerable number of genera based on
isolated plates, to which I refer later. The chief genera which occur
in these beds are also found in the Santa Cruz, and the distinguishing
features are as follows:
===================================================================
| Cephalic | Movable | Pelvic | Ornament-
| Shield | Plates | Buckler | ation
-------------+-------------+-------------+----------+--------------
Proeutatus |Plates thin, |Plates thick,| 8 + |“Flask”
| coarsely |⅓ overlapped |probably | figure
| pitted | | 10 rows |
-------------+-------------+-------------+----------+--------------
Prozaedius |Plates thin, |14 bands, |8 rows |3 long ridges,
| finely | thin, | | median ridge
| pitted |¼ overlapped | | narrow
-------------+-------------+-------------+----------+--------------
Stenotatus |Plates thick,|Plates |11 rows |3 long
| coarsely | thick | | ridges,
| pitted | and wide | | all
| | | | subequal
-------------+-------------+-------------+----------+--------------
Proeuphractus| |¼ overlapped |No buckler|
-------------+-------------+-------------+----------+--------------
Peltephilus |19 or 21 |Wide and thin|Buckler |Large
| Plates | 2-4 wide | | shallow
| 2 or 4 | | | pits
| horns | | |
-------------+-------------+-------------+----------+--------------
=Proeutatus= Ameghino
Eutatus Amegh., in part, 1887, Bol. Mus. La Plata, t. 1, p. 25.
Proeutatus Amegh., 1891, Revista Argen. d. Hist. Nat., t. 1, p. 327.
Thoracotherium Mercetat, 1891, Revista Mus. La Plata, t. 2, p. 42.
Eutatus Lydekker, in part, 1894, Anal. Mus. La Plata, t. 3, p. 62.
Proeutatus Scott, 1903-5, Reports Princeton Patagonian Exp.,
vol. 5, p. 40.
This is the most frequently occurring genus in the Deseado, but is as
yet represented only by isolated plates. The genus is distinguished
by thick, relatively long and narrow, movable plates, each overlapped
by about a third of its length. The plates of the pelvic buckler are
shorter and thicker, the exposed surface of each being ornamented by a
figure compared by Ameghino to a flask (see fig. 131), which figure is
more distinct on the rear, fading away toward the front. On the plates
of the pelvic buckler this figure is more accentuated, and from it, on
either side, radiate two furrows dividing the surface into several (4
to 5) areas. The entire surface of each plate is irregularly punctate.
=Proeutatus lagenaformis= Ameghino
P. sp? Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 660.
P. lagenaformis Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 507.
[Illustration: Fig. 131. _A_, movable plate; _B_ and _C_, plates from
pelvic buckler—natural size.]
On the Chico del Chubut River, west of Puerto Visser, we found nine
specimens of this species, all fragmentary, though one consists of over
fifty more or less broken plates, mostly from the pelvic buckler. This
is the only species of the genus from the Deseado, and corresponds to
the description above. A movable plate generally measures about 28
mm. long by 10 mm. wide, and has four large piliferous pits on the
posterior margin. A plate of the pelvic buckler varies greatly in
size, but is always thick and has two to eight piliferous holes on the
posterior margin. A typical plate measures 20 mm. long by 10 mm. wide.
=Prozaedius= Ameghino
Zaedius Amegh., in part, 1889, Act. Acad. Nac. Cordoba, t. 5, p. 867.
Prozaedius Amegh., 1891, Revista Argen. Hist. Nat., t. 1, p. 327.
Dasypus Lydekker, in part, 1894, Anal. Mus. La Plata, t. 3, p. 55.
Prozaedius Scott, 1903-5, Reports Princeton Patagonian Exp., vol. 5, p.
69.
Of this little genus, which is so strikingly like the living _Zaedius_,
we found a carapace with ten rows of movable plates in place, parts
of four rows of fixed plates from the pelvic buckler, and some caudal
vertebrae. The genus is distinguished by its thin plates, there being
fourteen bands of movable plates, and eight rows in the pelvic buckler.
The movable plates are narrow, each overlapped about a fourth of its
length, and have a faint ornamentation, with no piliferous pits except
on the posterior margin. The fixed plates are similar, except that they
are shorter, and have the ornamentation more accentuated, with radial
grooves. Ameghino has described three species as follows:
P. impressus, sculpture little accentuated, post. piliferic pits
rudimentary.
P. planus, sculpture more accentuated, post. piliferic pits lacking.
P. tenuissimus, very small.
In my specimen, the two anterior rows of movable plates lack the
marginal piliferous pits, on the next two rows they are rudimentary
(which is also true of the lateral plates even further back), while
on the bulk of the movable plates and on those of the pelvic buckler
there are two, three or four good-sized piliferous pits on the rear.
I can therefore recognize but two species, _P. impressus_ and _P.
tenuissimus_.
=Prozaedius impressus= Ameghino
P. impressus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 508.
P. planus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 509.
Our specimen was found on the Chico del Chubut River, west of Puerto
Visser, and preserves over two hundred plates, and eight caudal
vertebrae. The anterior rows of plates of the carapace consist of
thin plates overlapping about a fourth their length. Just behind
the overlap, there is, on each, a group of small punctations, and
the exposed part of the surface is divided by two shallow furrows,
making three more or less equal ridges which die out toward the rear,
leaving the posterior part of the plate plain. These most anterior
plates are bent to one side and have no piliferous pits on the rear
margin. The plates of the third and fourth rows are not bent, and
have the sculpture more distinct, the extreme lateral plates having
no piliferous pits, the median lateral plates with rudimentary
piliferous pits, and the dorsal ones with well marked posterior pits.
In each succeeding row toward the rear, the plates are more distinctly
ornamented and have larger posterior marginal pits. I have no marginal
plates.
[Illustration: Fig. 132. Portion of carapace—natural size; unshaded
plates are from cast; _a_ and _b_ plates from pelvic buckler.]
The plates of the pelvic buckler do not overlap, are shorter, have a
very distinct figure, and, in addition to the longitudinal furrows,
have a couple of radial furrows on either side, which divide the plate
into four or five areas (see fig. 132 a and b).
The caudal vertebrae are short and thick, indicating a short tail. I
found no plates which would indicate a caudal shield, which coincides
with the experience among the Santa Cruz specimens. The figures are to
scale and give most of the measurements.
There are ten rows of movable plates, probably two to three rows
lacking.
There are twenty + plates to a row.
A typical movable plate measures 17 mm. long by 6 mm. wide.
There were at least four rows in the pelvic buckler, probably eight as
in the Santa Cruz.
A typical fixed plate measures 10 mm. long by 5 mm. wide.
=Prozaedius tenuissimus= Ameghino
P. tenuissimus Amegh., 1902, Bol. Acad. Nac. Cienc. Cordoba, t. 17, p.
66.
This species is characterized by Ameghino on account of its small size.
The movable plates have two furrows which converge toward the front,
and between which is a median crest. In the furrows are two rows of
perforations. A movable plate measures 9 mm. long by 4 mm. wide.
=Stenotatus= Ameghino
Euphractus Ameghino, in part, 1887, Bol. Mus. La Plata, t. I, p. 26 of
separate.
Dasypus Amegh., in part, 1889, Act. Acad. Nac. Cienc. Cordoba, t. 5, p.
864.
Stenotatus Amegh., 1891, Revista Argen. Hist. Nat., t. I, p. 253.
Dasypus Lydekker, 1894, Anal. Mus. La Plata, t. 3, p. 55.
Prodasypus Amegh., 1894, Bol. Acad. Nac. Cienc. Cordoba, t. 13, p. 172
of separate.
Stenotatus Scott, 1903-5 Princeton Patagonian Exped., vol. 5, p. 80.
The genus is very like _Prozaedius_ but differs in having thicker
and wider movable plates, in having more rows of plates in the pelvic
buckler (11), and in details throughout the skeleton. We found no
representatives of the genus, but Ameghino has described a species (no
figure), S. (_Prodasypus) ornatus_[22] based on isolated plates. A
movable plate measures 18 mm. long by 6-7 mm. wide, while a fixed plate
measures 9 mm. long, by 6-7 mm. wide.
[Footnote 22: Bol. Inst. Geog. Argen., t. 18, p. 508, 1897.]
=Proeuphractus= Ameghino
Proeuphractus Amegh., 1886, Bol. Acad. Nac. Cienc. Cordoba, t. 9, p.
208.
This genus is seldom found, but is distinguished by Ameghino by the
absence of a pelvic buckler, all the plates of the carapace being
movable. From the Deseado beds, Ameghino describes two species, _P.
setiger_ and _P. laevis_, both based on isolated plates; the former
distinguished by having no piliferous perforation in the furrows
surrounding the central figure, and with well-developed pits on the
posterior margin; while the latter has small piliferous perforations in
the furrows and only rudimentary ones on the posterior margin. These
features do not seem to me to distinguish species.
In addition to the foregoing, Ameghino has made a series of genera and
species,[23] _Archaeutatus_, _Amblytatus_, _Isutaetus_, _Sadypus_,
_Hemiutaetus_, _Anutaetus_, all based on isolated plates, and
distinguished by variations in the central figure and the piliferous
pits. I am unable to find a satisfactory basis for distinguishing the
genera or species, and feel that, until more complete material is
known, it is impossible to say which are valid genera or species.
[Footnote 23: Bol. Acad. Nac. Cienc. Cordoba, t. 17, p. 56-66, 1902, no
figures.]
=Peltephilus= Ameghino
Peltephilus Amegh., 1887, Bol. Mus. La Plata, t. 1, p. 25 of separate.
Cochlops Amegh., in part, 1889, Act. Acad. Nac. Cienc. Cordoba, t. 5,
p. 792.
Gephyranodon Amegh., 1891, Revista Argen., Hist. Nat., t. 1, p. 119.
? Anatiosodon Amegh., 1891, Revista Argen. Hist. Nat., t. 1, p. 327.
Peltephilus Scott, 1903-5, Princeton Patagonian Exped., vol. 5, p. 88.
While rare, this genus is well known from the Santa Cruz, and is
characterized by the curious development of the head shield, which
consists of nineteen or twenty-one definitely arranged head plates, the
anterior ones being developed into horn-like projections. The plates
of the carapace are wide, thin, and unique in each having two to four
wide shallow pits on the exposed surface. We found the genus rare, only
two isolated plates turning up. From the Deseado material Ameghino has
made three species: _P. protervus_, of very large size; _P. undulatus_,
of moderate size, with the median figure accentuated and ending in two
pits and with piliferous depressions on the margin; and _P. depressus_,
of the same size as the foregoing, with a faint central figure, often
four pits on the exposed surface and no piliferous pits on the margin.
We found but one species, one plate of which combines characters of
both the last two as described, so that I feel that there should be but
two species, _P. protervus_ and _P. undulatus_.
=Peltephilus undulatus= Ameghino
[Illustration: Fig. 133. Two movable plates—natural size.]
P. undulatus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 509.
P. depressus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 510.
One of the plates we found has the rough surface, obscure figure, two
pits on the median part of the surface, and marginal piliferous pits,
of which the first two features are characters of _P. undulatus_,
the last is the feature of _P. depressus_, so I have combined the
two species. A second plate does not have the marginal pits but is
otherwise the same. I expect considerable variation in the pattern on
plates from different regions of the carapace.
=Peltephilus protervus= Ameghino
P. protervus, Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 509.
This species, of which we found no representative, is very large. The
plates of the type have two pits on the anterior part of the exposed
surface and none on the margin. A movable plate measures 41 mm. long by
22 mm. wide. One of the horn-like plates from the cephalic shield is 35
mm. long, by 30 mm. wide, and has a height of 44 mm.
GLYPTODONTIA
This suborder is most sparingly represented, apparently on account
of unfavorable habitat. Ameghino has described a few fragments of
the carapaces of these forms, making the genera, _Palaeopeltis_, and
_Glyptatelus_, both pre-Santa Cruz genera.
=Palaeopeltis= Ameghino
Palaeopeltis Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 659.
The basis of this genus is a few plates of a glyptodon-like animal of
considerable size, but the plates are without ornamentation. This form
Ameghino considers intermediate between glyptodonts and armadilloes.
I feel that there is too little of the skeleton known to justify this
conclusion, especially as glyptodonts of a considerably higher grade of
specialization are contemporaries of this form.
[Illustration: Fig. 134. P. inornatus: a single plate—natural size.]
=Palaeopeltis inornatus= Ameghino
P. inornatus Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 659.
P. inornatus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 506.
The species is founded on four plates which are without ornamentation,
and externally smooth except for numerous vascular perforations. They
are of considerable size and entirely characteristic. The one such
plate which we found is shown in fig. 134.
=Glyptatelus= Ameghino
Glyptatelus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 507.
The plates of the carapace are similar to those of _Palaeohoplophorus_,
the O-figure being, however, nearer the rear of each plate, and the
number of radial furrows being smaller, usually six. We found no
specimens of this interesting form. Ameghino has made two species, _G.
tatusinus_ and _G. malaspinensis_.
=Glyptatelus tatusinus= Ameghino
G. tatusinus, Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 507.
I reproduce Ameghino’s figure of this species which shows all that is
known of the form.
[Illustration: Fig. 135. Four plates—natural size, after Ameghino.]
=Glyptatelus malaspinensis= Ameghino
G. malaspinensis Amegh., 1902, Bol. Acad. Nac. Cienc., Cordoba, t. 17,
p. 50.
This species is described (no figure) as about the same size as the
preceding, but with subordinate figures in the central O-figure, and
also outside of it. A dorsal plate measures 26 mm. long by 20 mm. wide.
GRAVIGRADA
Remains of this suborder are almost as rare as those of the
glyptodonts, and apparently for the same reason, unfavorable habitat.
We found no remains of this group, but Ameghino has described a skull
and some teeth as belonging to this group; so, in order to present a
complete view of the Deseado fauna, I give a digest of his descriptions.
=Hapalops antistis= Ameghino
H. antistis Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 505.
The species is based on a skull, not figured, of which Ameghino says:
the size is small, the molars are compressed from front to back, and
gives the following measurements:
Length of cranium from front of max. to occ. condyles 140 mm.
Length of four post, molars 27 mm.
Distance from front of max. to back of last molar 48 mm.
=Octodontotherium= Ameghino
Octodontotherium Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 656.
The genus is based on isolated teeth, each a mass of dentine surrounded
by a thin layer of cement. The anterior tooth of the upper jaw is
caniniform, the first molar ovoid in section, the last molar is
bilobed, corresponding to _Pseudolestodon_. The first tooth of the
lower jaw is also caniniform, but is two-faced as a result of wear. The
intermediate upper and lower molars are rectangular prisms resembling
those of _Chlamdotherium_.
=Octodontotherium grandis= Ameghino
O. grandis Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 656.
O. grandis Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 505.
In addition to the above, Ameghino simply gives the following
measurements:
First upper tooth, ant.-post. diam. 20 mm.,
trans. diam. 13 mm., height 80 mm.
First lower tooth, ant.-post. diam. 21 mm.,
trans. diam. 16 mm., height 80 mm.
Last lower tooth, ant.-post. diam. 28 mm.,
trans. diam. of ant. lobe 18 mm.
Last lower tooth, trans. diam. of post. lobe 16 mm.,
median diam. 7 mm.
[Illustration: Fig. 136. _A_, lower molar, side view—natural size;
_B_, lower molar, cross section—natural size; _C_, upper molar, cross
section—natural size, after Ameghino.]
=Octodontotherium crassidens= Ameghino
O. crassidens Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 505.
This second species is based on isolated teeth of larger size than the
preceding, with measurements as follows:
Upper molar, ant.-post. diam. 26 mm., trans. diam. 18 mm.
Lower molar, ant.-post. diam. 26 mm., trans. diam. of ant. lobe
21 mm., trans. diam. of post. lobe 16 mm.
=Orphodon= Ameghino
Orphodon Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 658.
Orphodon Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 504.
The teeth of this type are a mass of dentine, each surrounded by a
thin layer of cement, and each tooth subcylindrical in section, with
the crown worn to two apposed oblique planes. The genus resembles
_Ortotherium_.
[Illustration: Fig. 137. Type—natural size, after Ameghino.]
=Orphodon hapaloides= Ameghino
O. hapaloides Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 658.
O. hapaloides Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 505.
In addition to the above, Ameghino gives a figure, here reproduced, and
the following measurements: Tooth, greatest diam. 12 mm., lesser diam.,
10 mm.