334 
C.J. Burrow 
anterior and posterior ends are broken; the base is 
transversely concave. The main tooth row extends 
along the lateral edge of the occlusal surface of the 
jawbone, and comprises a series of five 
multicuspidate teeth which increase in size and 
number of side cusps posterior to anterior. The 
main cusps are sub-triangular in parabasal section, 
with the 'angles' positioned anteriorly, posteriorly 
and medially. The posterior teeth are low and 
worn, with side cusps barely discernible. The 
anterior teeth are formed by a main cusp and one 
medial, three anterior and two or three posterior 
cusps. The main tooth row is separated by a deep 
channel from a medial tuberculated ridge, which 
bears approximately 40 irregularly clustered 
tubercles varying from less than 0.1 mm wide to 
0.5 mm wide at the base, and with from five to 13 
or more radiating ribs. They have worn, rounded 
apices, and are directed medially or vertically. The 
ridge diminishes in height from 0.8 mm posteriorly 
to 0.4 mm at the anterior limit of the tubercles. 
The other two fragments are shorter, but of 
comparable depth and robustness. If all three 
fragments had originally been positioned on the 
lower jaw, two are from the left side and one from 
the right side. A vertical, transverse, ground thin 
section was made of one of the fragments 
(MMMC02276, Figure 6A). Wide, vascular canals 
extend throughout the bone base, and up into the 
main cusp. Denteons surround some of the canals, 
with bone cell lacunae between the denteons. 
Orthodentine tubules are present in the large 
tubercle of the medial ridge, and in the upper 
section of the main tooth cusp. 
Anterior jaw fragment (Figure 3E) 
This fragment (MMMC02278) is 1.5 mm long, 
and has one almost complete tooth 'group' (i.e., a 
main cusp plus side cusps) with one large cusp, 
three posterior side cusps and two anterior side 
cusps. The distal surface of the jaw fragment is flat. 
The posterior cusps are overlapped laterally by the 
anterior cusps of the next tooth group. The main 
cusp is 0.6 mm high with a sub-triangular 
parabasal section, and the smaller cusps are about 
0.15 mm high, and laterally flattened with an 
elliptical parabasal section. 
The other six fragments range from 1.4 to 2.0 mm 
long, including a very robust fragment with a main 
cusp that is 2.0 mm high. It is not possible to 
determine the original orientation of most of the 
fragments. Figure 6B is of a vertical, longitudinal, 
ground thin section of a fragment (MMMC02274) 
with one main cusp and three side cusps, and 
illustrates the highly vascular structure of the bone 
base and main cusp. The secondary cusps are less 
vascular, and are formed of a relatively dense, 
dentinous tissue. Separation between the lateral 
ridge tissue and the central tissue of the main cusp 
is clearly delineated. 
Symmetrical tooth whorl (Figure 4A) 
In crown view, the base of this specimen 
(MMMC02249) is sub-triangular in outline, being 
0.7 mm wide posteriorly and narrowing to a 
rounded point anteriorly. The base is arched, and 
is concave anterior to posterior. The crown has 
four tooth rows, with the cusps decreasing in size 
to the front. Each row has a prominent central 
cusp, the largest being 0.5 mm high; on each side 
there are up to four subsidiary cusps, 
approximately a quarter of the height of the central 
cusp. The central, or main, cusps have sub- 
triangular parabasal sections, with the angles 
pointing anteriorly and laterally. The three ridges 
which contribute to this triangular cross section 
differ in appearance from the central cusp area, 
being coloured white whereas the rest of the cusp 
is amber. 
The other 12 tooth whorls of this type range 
greatly in size and relative robustness of the cusps 
and base: the smallest is 0.4 mm long and high, 
while the largest is over 2.0 mm long with a central 
cusp nearly 2.0 mm high. The tooth whorls 
comprise from three to six tooth rows; on some, 
the main cusp is only about twice as high as the 
side cusps, while on others the main cusp is up to 
four times as high (e.g., toothwhorl MMMC02256, 
Figure 4B,C). The number of cusps per tooth row is 
also variable, with from two to six or more side 
cusps. The number of side cusps varies 
independently of the size of the tooth whorl. One 
of the tooth whorls (MMMC01962, Figure 4G), 
while having the same generalized form as the 
other tooth whorls in this category, has a 
'segmented' base corresponding to its tooth rows. 
In Figure 6C, a vertical, rostro-caudal, ground thin 
section of tooth whorl MMMC02275, central 'pulp 
canals' of the main tooth cusps are clearly visible, 
with fine orthodentine tubules radiating obliquely 
from them. Bone cell lacunae appear to be 
concentrated in the bone base. 
Single tooth (Figure 5A) 
The slightly recurved tooth (MMMC02277) is 0.7 
mm high and has a base diameter of 0.3 mm. It has 
a narrow conical shape, with a hollow base of 
circular cross section, and a rounded apex. The 
tooth has a ring of small cusps approximately 0.4 
mm from the tip, and has the dull appearance of 
bone below this ring, whereas it is shiny and 
dentinous above it. 
The other 13 teeth are all of a similar size and 
shape. 
Dentition cone, type I (Figure 5B) 
This element (MMMC02252) is a hollow, thin- 
walled, bisymmetrical cone, 1.0 mm high, with a 
base diameter of 0.35 mm. It is characterised by an 
apex to base line of oblique spiny denticles. The 
