Plate 7
Temnodontosaurus eurycephalus, holotype, BMNH R1157. Scale measures 100 mm.
are any consistent differences between the relative lengths
of the fore and hindfin. Consequently, Blake’s (1876) distinguishing
feature is not helpful. The specimens referred
to T. crassimanus (WM 2546S, WM 5, and the holotype)
appear to differ from T. platyodon and T. trigonodon sufficiently
to warrant retention of Blake’s (1876) taxon, at least
for the present.
Temnodontosaurus eurycephalus McGowan, 1974A
Fig. 77F; PI. 7
Ichthyosaurus breviceps Owen 1881: 109 [partim]
Ichthyosaurus platyodon C onybeare; L ydekker 1889A: 98
[partim]
Eurypterygius breviceps; H uene, 1 9 2 2 :8 , pi. 1, fig. 3 [referred
to in the figure legend, in error, as Eurypterygius brevi-
rostris (Owen)]
Temnodontosaurus eurycephalus McGowan, 1974A: 20
Holotype: BMNH R1157, a complete skull.
Diagnosis: Short, broad, rostrum, snout ratio <0.58; orbit
relatively small, orbital ratio <0.21; maxilla relatively long,
premaxillary ratio <0.36 and probably <0.30; teeth robust;
skull and mandible both deep. Large, skull length >500 mm.
Occurrence: Lyme Regis, Dorset, England.
Stratigraphic range: The holotype was collected from the
zone of Arietites bucklandi and is therefore from the lowermost
Sinemurian.
Remarks: Although confused with Ichthyosaurus breviceps
in the past, the two are readily distinguishable. 1. breviceps.
has a gracile skull, in marked contrast to the robust skull of
T. eurycephalus, which is about four times larger than that
of the largest individual of I. breviceps. Furthermore, whereas
the large orbit dominates the skull in I. breviceps, the
orbit is relatively small in T. eurycephalus.
Temnodontosaurus acutirostris (Owen, 1840)
Fig. 78
Ichthyosaurus-, Y oung & Bird, 1822: pi. 16, fig. 4
Ichthyosaurus acutirostris Owen, 1840: 121
Ichthyosaurus longipennis Mantell, 1851: 378
Ichthyosaurus acutirostris;• P hillips, 1875: 272
Ichthyosaurus acutirostris; Blake, 1876: 253
Ichthyosaurus zetlandicus Seeley, 1880: 635
Ichthyosaurus acutirostris-, Owen, 1881: 121
Stenopterygius acutirostris-, McGowan, 1974A: 2 7
Holotype: BMNH 14553, comprising a skull (Owen, 1881:
pi. 28, fig. 2 ), one complete forefin with a few proximal
elements of the other one, a coracoid and other parts of the
pectoral girdle, and several ribs, as recorded by L ydekker
(1889A: 73-74). The specimen has since lost the anterior
part of the snout.
Diagnosis: Teeth numerous, with no tendency toward reduction
in size or number. Snout long, slender, probably
tapering to sharp point, snout ratio usually >0.64; orbit
small, orbital ratio <0.24; premaxillary ratio probably
<0.42. Forefin probably elongate, number of elements in
longest digit maybe >30; notching occurs, probably restricted
to only a few proximal elements. Moderate sized
ichthyosaurs, skull probably <1 m.
Occurrence: Whitby, Yorkshire, England.
Stratigraphic range: Upper Lias; Lower Jurassic (Toar-
cian).
Remarks: Owen’s (1881 r pi. 28, fig. 2) figure, which is
redrawn here (Fig. 78), shows a complete skull, exposed
from the right side, whereas the left side of the skull is
exposed in BMNH 14553. However, it was not unusual for
Owen to depict figures laterally inverted. For example,
immediately beneath his figure of the holotype skull,
Owen (1881: pi. 28, fig. 3) figured a skull of Leptonectes
tenuirostris (BMNH 36182) that is laterally inverted. Ly-
dekker’s (1889A) description of BMNH 14553 agreed with
Owen’s figure, stating that the right lateral aspect of the
skull was exposed, but he too is known to have made such
errors. The remainder of L ydekker’s (1889A) description,
which includes reference to the remarkably long forefin, is
accurate, so there is little doubt that BMNH 14553 is the
holotype. The snout was lost some time after the material
was first figured and described, so the specimen bears little
resemblance to Owen’s idealized drawing of the skull.
This figure depicts a down-curved snout, and, although
some specimens, such as BMNH 15500a, have this feature,
it may be a preservational artifact due to dorsoventral
compression of the slender rostrum.
The most striking feature of the holotype is the extreme
length and slenderness of the forefin, which has approximately
30 elements in the longest digit. Owen made no
reference to this singular feature, either in his brief original
description (1840) or in his later treatment (1881), nor was
the fin figured. The forefin is currently being investigated
to determine its authenticity (Chapman and Doyle, in
preparation). Its characteristic elongation is therefore only
provisionally included in the diagnosis. There are four
digits, and notching occurs in the radius and in the next
two, possibly three elements.
Y oung & Bird (1822, 1828) described ichthyosaurian
material from the vicinity of Whitby. Most of it was said to
be referable to Ichthyosaurus communis, whereas some of it
could be assigned to I. platyodon and I. tenuirostris. They
also referred to some large vertebrae “measuring about
seven inches in diameter” and portions of “paddle bones,
scapular bones, &c. [etc.], of vast size”, which, if “of the
Ichthyosaurus family, we may well name it I. giganteus”
(Young & Bird, 1822:285). These elements are probably too
large to be referable to T. acutirostris.
Seeley (1880) erected I. zetlandicus on a large, partial
skull from Whitby (SMC J35176). Aside from its incompleteness,
the specimen is well preserved and three-dimensional,
which is most unusual for ichthyosaurs. This
was probably the reason Seeley (1880, p. 646) wrote: “I am
acquainted with no other ichthyosaur in which the skull
attains this broad, triangular form, with the orbits so far
apart ... with the nares so far in front of the orbits and
relatively so large. ... These characters sufficiently distinguish
the species from all others.” Because of its incompleteness,
few comparisons can be made with specimens
that have been referred to T. acutirostris. As there are no
inconsistencies, and as it is from the same locality, the most
appropriate course is to synonymize I. zetlandicus with
T. acutirostris.
Because of poor preservation the Whitby material is
not well known. None of the referred specimens has a
determinate pelvis, making the generic assignation uncertain.
(A single Whitby specimen (WM 876S) with a determinate
pelvic girdle [pubis and ischium fused], has degenerate
teeth, and a preflexural vertebral count of approxi