Name: Brachiopoda;
Heliomedusa orienta (Chengjiang)
Age: Early
Cambrian (~525 million years ago)
Size (25.4mm=1
inch): 13 mm by 17 mm on a 25 mm by 33 mm and 65 mm by 75 mm matrix pair
Location:
Quiongzhusi Section, Yu’anshan Member, Heilinpu Formation , Mao
Tian Hill, Yuxi, Chengjiang County, Yunnan Province, China
|  Description:
This brachiopod is known as Heliomedusa orienta. The species is
a relatively common member of the Chengjiang biota. The source of
the specific name is easy to determine, but the reason is that the
oval shape and redial patterning led the original describers to
think it was a jellyfish.. The diversity of soft-tissue fossils
is astonishing: algae, medusiforms, sponges, priapulids, annelid-like
worms, echinoderms, arthropods (including trilobites), hemichordates,
chordates, and the first agnathan fish make up just a small fraction
of the total. Numerous problematic forms  are
known as well, some of which may have represented failed attempts
at diversity that did not persist to the present day. Unlike most
brachiopods, Heliomedusa lacked a pedicle, leading scientists to
believe it lay upon the surface of the sediment as an epifaunal
filter feeder. Notice the fringe of setae thought to have served
a sensory function. Note too the dark U-shaped structure contained
within the shell. This is the lophophore, the structure by which
the brachiopod circulated water for respiration and to extract food.
Even the growth lines in the shell are readily discerned.
|
|
