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50
Si 5
15i
10-
5-
20
J 15
I 10
f 5
Humeri Femora
•i.llllll.
73 75 77 79 81 83 85
Length mm
Ulnae
I.I.I
73 75 77 79 81 83 85
Length mm
Carpometacarpi
•••••••I.I I" i" i~ i — i — i — i r*~i—•—i
36 37 38 39 40 41 42
Length mm
a 4
I
SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
15-
JUV
10-
26.5 27.5 28.5 29.5 30.5 31.5
Length mm
Tibiotarsi
• -III.
• i
48 50 52 54 56
15-,
g 10
o
3
| 5
u.
0
Length mm
Tarsometatarsi
• -Mil..
31 32 33 34 35 36
Length mm
FIGURE 8.—Histograms of lengths of Pterodroma mollis bones from Amsterdam Island
more robust than in the similar-sized P. neglecta. Pterodroma
baraui differs from P. arminjoniana in that the ventral process
of the os lacrimale, where it descends from the os ectethmoidale,
is much shorter, with a different shape of the articular facet.
The lower fonticulus orbitocranale is more elongate in P
baraui {n=3, 5.8 mm high x 9.1 mm long, 6.0 x 8.6 mm, 6.0 x
8.8 mm, vs. 6.5 x 7.7 mm in P. arminjoniana). The fossil cranium
from site 8.11 has a basicranial length of 37 mm but is too
broken to measure further; however, the extensive temporal
fossae, lacrimal shape, and shape of the fonticulus orbitocraniale
clearly identify it as P baraui. The posterior portion of the
cranium from site 8.3 (width at zygomatic processes 25.5 mm)
has wide temporal fossae like P. baraui and is referred to that
species. The postcranial bones in P. baraui and P. arminjoniana
are very similar, and subtle differences, if present, between
them would not be of use in identifying fossil material that is
worn, weathered, or broken. Because all cranial material from
site 8 is referred to P. baraui, all the postcranial bones of midsized
Pterodroma from this site also are referred to that species
(Table 3). This is further supported by the tarsometatarsi from
site 8, which are similar to those of P. baraui (Table 4) and are
shorter and stouter than those of P. macroptera.
TABLE 3.—Summary statistics for bones attributed to fossil Pterodroma baraui
and measurements (mm) of intermediate-sized fossil Pterodroma species,
Amsterdam Island.
Species
P. baraui
mean
standard deviation
minimum
maximum
sample size
P. arminjoniana/
baraui
site 18.1
site 18.27
site 18.26
P. arminjoniana
site 18.2
site 18.8
site 18.11
Fern L
32.87
0.05
32.83
32.9
2
-
-
-
-
-
-
TmtL
38.14
0.06
38.1
38.18
2
-
-
-
-
-
-
HumL
91.82
1.82
90.4
94.32
4
-
95.4
95.8
-
89.7
91.5
Pterodroma sp.
UlnaL
97.42
1.99
95
102.5
13
96.8
- -
97.3
-
-
Cmc L
47.62
1.36
46
50.1
9
-
- -
- -
-
CorL
26.07
0.42
25.6
26.43
3
Two premaxillae (MNZ S34852, MNZ S34859) are very
short and stout and are not referable to any of the above species.
Bourne (1968) gave measurements for a premaxilla of the
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