JURASSIC DINOSAUR FAUNAS IN ZIGONG - 自贡恐龙博物馆

scapula longer than femur; sternum small and subcircular-shaped; forelimb about 3/4 ~ 4/5 of
length of hindlimb; and small manus and pes.
Type species Mamenchisaurus constructus Young, 1954.
Mamenchisaurus youngi Pi et al., 1996
Diagnosis Medium-sized mamenchisaurid about 16 m of body length. It is recognized by
a very light-built skull with large external openings and a V-shaped dorsal view; external naris
dorsolaterally situated in mid-skull; pear-shaped orbit and triangular antorbital; length of
infratemporal fenestra equals to its height; posterior cranial roof inclined backward; quadrate
extending anteroventrally; large maxilla and premaxilla forming relatively broad facial region;
lachrymal, postorbital and quadratojugal slender; occipital ridge of supraoccipital well developed;
long dentary with a remarkable droopy anterior end; external mandibular foramen slightly
posteriorly positioned; long dentary dentition containing much more teeth; dental formula Pm4 +
M18 / D23~24; spoon-shaped teeth with slender crowns; tooth crown with prominent wear facet;
serrations of anterior margin more than posterior margin in unworn teeth; 18 cervicals, 12 dorsals,
5 sacrals and more than 50 caudals; opisthocoelous presacral centra with developed cellular
structures but simple laminar structures; neural spines of posterior cervicals and anterior dorsals
slightly bifurcated; longest cervical centrum 2.5 times of length of longest dorsal centrum;
cervical centra with undeveloped pleurocoel and lacking ventral keel; extremely slender cervical
ribs; middle cervical ribs with a forked anterior process; dorsal centra with a slightly developed
pleurocoel; all sacral centra and first four sacral neural spines co-ossified; anterior caudals
strongly precoelous and distal caudals amphiplatyan; long and broad scapula; small sternum; low
and elongate ilium with developed anterior process and pubic peduncle; humerus almost 72% of
femur length; ulna about 69% of humerus length; tibia about 57% of femur length; small manus
and pes; only manual digit I with an ungual; manual digit formula 2-2-1?-1?-1?; pedal digit I and
II with unguals; and pedal digit formula 2-3-3-2?-1?.
Holotype A nearly complete skeleton including nearly complete skull and lower jaws, 18
cervicals, 12 dorsals, 5 sacrals, 14 caudals, many ribs and chevrons, nearly complete girdles and
limbs, and a piece of skin impression. ZDM 0083.
Locality and horizon Jiujingba, Xinmin, Zigong; Shangshaximiao Formation, Late
Jurassic.
Mamenchisaurus hochuanensis Young et Chao, 1972
Revised diagnosis Huge mamenchisaurid about 20~22 m of body length. It is recognized
by light-built skull; small and spoon-shaped teeth with well serrated anterior and posterior
margins; dental formula Pm4 + M18 / D19; 19 cervicals, 12 dorsals, 4 sacrals and more than 50
caudals; presacrals opisthocoelous; neural spines of posterior cervicals and anterior dorsals
slightly bifurcated; extraordinarily elongated cervicals with longest centra about 3.3 times of
average length of dorsal centra; dorsal centra with well developed pleurocoels; robust dorsal ribs
with broad distal end; anterior caudals precoelous and distal caudals amphiplatyan; last several