Ptaiochen, new genus
Type species:Ptaiochen pau, new species.
Included species:Type species only.
Distribution: Maul
Etymology: Greek, ptaio, stumble, and chen, goose; so named for the propensity
of the species to fall into holes. The gender is masculine.
Diagnosis: Similar to Thambetochen in having both jaws with bony toothlike
projections, while lacking the very deep rostrum of Chelychelynechen. Differs
from Thambetochenin having the rostrum proportionatelys horter, the nostrils
situated farther anteriorly, with the rostral tip anterior to the nostril being much
shorter. The midline groove on the palatal surface of the rostrum is deeper and
wider. The prefrontals (lacrimals) are much better developed, extending ventrally
and posteriorly towards the equally well developedp ostorbital processess o as to
come much closer to encircling the orbit than in Thambetochen. The roof of the
orbits is not expanded laterally and the ventral surfaces do not contain impressions
for salt glands as in Thambetochen. The temporal lossac and the scars for attachment
of the dorsal neck musculature are much less extensive than in Thambetochen,
whereas the scar for M. depressor mandibulae is deeper and wider. The
overall outline of the cranium in lateral and posterior views is more rounded,
rather than being flattened dorsally and squared in posterior view as in Tharnbetochen.
The mandible has a much shorter symphysis, with the dorsal surface of the
dentary flattened and expanded, though not nearly to the extent as in Chelychelynechen,
and the tooth-like projections along the inner margins of the dentary
are very reduced compared with Thambetochen. The lateral protuberance of the
coronoid process is better developed and more dorsally situated than in Thambetochena,
lthougha gain not to the degreet hat it is in Chelychelynechen.
The coracoidi s proportionatelyl onger,s traighter,a nd hast he sternale nd much
lesse xpandedt han in either Tharnbetocheno r ChelychelynechenT.h e head of the
femur is angled much more proximally, well above the level of the trochanter,
than in Tharnbetochen. The fibula has a distinct squared crest on the anterior
margin.T he syringeabl ulla is larger,m ore inflated,a nd differsi n shapef rom that
of Tharnbetochen(F ig. 8).
Remarks: Although clearly related to Tharnbetocheno n the basis of bill morphology,
t he differencess hownb y Ptaiochena re consistenwt ith recognizingth is
moa-naloa s a distinctg enus.S omeo f the characterso f the mandiblei n particular
suggest hat Chelychelynechenm ay have been derived from an ancestorm ore
similar to Ptaiochen than Tharnbetochen. On the other hand, the coracold in
Chelychelynecheins more like that of Tharnbetochena nd dissimilar to that of
Ptaiochen.
Ptaiochen pau, new species
(Figs. 1 lB, D, F, H, 12B, E, F)
"Maui Thambetochen sp. B" Olson and James, 1984:772.
Holotype: Associated cranium, rostrum, and mandible lacking the right postdentary
portion, USNM 384776 (Figs. 1 lB, 12B, E, F). Collected in September
1982 by Storrs L. Olson, Helen F. James and others.
Type locality: Auwahi Cave (1,145 m), Maui, Hawaiian Islands.
Distribution: Maui, southern slopes of Mr. Haleakala at upper elevations, from
1,145 m (Auwahi Cave) to 1,860 m (Kipahulu Valley).
Etymology: Hawaiian, pau, finished, ended, destroyed; in reference to the lamentable
extinction of the species.
Measurements (rnrn) of holotype: Rostrum: length from nasofrontal hinge to
tip, 48.7; height and width at posterior margin of nostril, 22.2 x 24.4; length of
nostril, 14.6, least width of internarial bar, 4.0; length from anterior margin of
nostril to tip, 22.9. Cranium: length from nasofrontal hinge, 55.0; greatest width
(acrossp ostorbitalp rocesses4),4 .4; width acrosss quamosals3, 9.5; greatesth orizontal
diameter of orbit, 22.7. Mandible: total length without retroarticular process,
65.6; symphysis length, 13.7; greatest width of dentary, 6.2; height at coronoid
process, 15.0.
Paratype:A ssociatedin completes keletonf rom the type locality,U SNM 322649;
very eroded cranium in two pieces; 5 presacral and 5 caudal vertebrae plus pygostyle;
e rodedp elvisl ackingm ost of the postacetabulairli a; right coracold( Fig.
11F); right and left scapulae (incomplete); right and left humeri (distal ends incomplete);
r ight and left radii and ulnae; right carpometacarpusr;i ght (Fig. 11H )
and left femora, tibiotarsi, fibulae (Fig. 11D), and tarsometatarsi; 16 pedal phalanges
plus 5 unguals; a few ribs and other fragments.
Measurements( rnrn)o fparatype:C oracoid:g reatestle ngth,3 0.2; depth through
scapular end, 10.4; width and depth of shaft just below glenoid facet, 4.6 x 4.6;
width at sternale nd, 13.6. Scapula:p roximal width, 10.2. Humerus:l ength,5 0.9;
shaft width and depth at midpoint, 5.3 x 5.0. Ulna: length, 33.1. Radius: length,
31.3. Carpometacarpusl:e ngth, 18.5. Pelvis: length of sacrum,c a. 110; width
across antitrochanters, ca. 51; greatest internal diameter of acetabulum, 10.4.
Femur: length, 89.3; proximal width and depth, 25.6 x 26. l; greatest diameter
of head, 11.4, shaft width and depth at midpoint, 10.5 x 9.9: distal width and
depth, 20.8 x 20.8. Fibula: proximal width and depth, 5.3 x 14.5. Tibiotarsus:
length from cnemial crest, 146; length from proximal articular surface, 138.8;
width of proximal articular surface, 21.9; length of fibular crest, 22.1; width and
depth of shaft at midpoint, 9.3 x 8.2; distal width and depth, 18.7 x 20.5.
Tarsometatarsus: length, 80.2; proximal width, 21.5; width and depth of shaft at
midpoint, 10.9 x 7.1; distal width, 22.4; depth of middle trochlea, 13.1.
Diagnosis: As for the genus.
Remarks: Ptaiochen pau appears to have been restricted to higher elevations.
Its lowest occurrence is at the type locality, Auwahi Cave (1,145 m), where it is
decidedlyl essa bundantt han ThambetochenA. t sitesa t highere levations,P taiochen
is the most common if not the only moa-nalo. At Puu Makua (1,463 m)
Thambetochenis rare by comparisona, nd in the Kipahulu Valley caves( 1,860 m)
Ptaiochen is the only mao-nalo identified. Altitudinal differences in the relative
abundances of anatids on a given island might explain the great rarity of the
"supernumerary goose" on Oahu, and the lack of a second species of moa-nalo
on Molokai, on both of which islands all fossil localities are just above sea level.
Storrs L. Olson & Helen F. James,
Descriptions of thirty-two new species of birds from the Hawaiian Islands: Part I. Non-Passeriformes
Ornithological Monographs 45 (1991)
The American Ornithologists' Union, Washington D.C.
elibrary.unm.edu/sora/om/om045.pdf
