(LINKS TO PAST FOSSIL FRIDAYS)
Community College (LRCCD)
Geology & Earth Science Instructor: Arthur
Reed, P.G.
Happy Fossil Friday!
Friday October 15, 2021
Fossils
of Giant Sea Scorpion Found in China
Life reconstruction
of Terropterus xiushanensis.
Image credit: Dinghua Yang.
Eurypterids,
normally known as sea scorpions, are an important extinct group of Paleozoic
chelicerate arthropods in Silurian seas about 430 million years ago. Mixopterids are a remarkable group of
eurypterids characterized by extremely specialized prosomal appendages. These
limbs were presumably used for prey-capture, like the “catching basket” formed
by the spiny pedipalps of whip spiders. However, in contrast with their
popularity, our knowledge of these bizarre animals is limited to only four
species in two genera, all described from Laurussia 80 years ago. Here, Wang et
al. described a new mixopterid, Terropterus xiushanensis from
the Lower Silurian period of South China.
See
the ‘paleo’ map below to see where they lived during the Silurian, and the
current image from Google Maps showing where these fossils ended up in modern
day China after 430 million years of plate movement.
A
science news article on the discovery by the site ‘sci-news.com’
is immediately below, and the recently published research can be viewed by
going to: ‘sciencedirect.com’.
Fossils of Giant Sea Scorpion Found in China
Oct 11, 2021
by Enrico de Lazaro
Terropterus
xiushanensis lived approximately
435 million years ago during the Llandovery epoch of the Silurian period.
The
ancient marine creature belongs to a family of sea scorpions called Mixopteridae.
“Eurypterids,
or sea scorpions, are an important group of mid-Paleozoic chelicerate
arthropods whose evolution and paleoecological significance have attracted much
attention in recent years,” said Professor Bo Wang from the Nanjing Institute of
Geology and Paleontology and Center for Excellence in Life and Paleoenvironment
at the Chinese Academy of Sciences and colleagues.
“One
of the most remarkable eurypterid families is Mixopteridae, whose members are
quite large and superficially scorpion-like eurypterids bearing highly
specialized anterior appendages.”
“Their
second, and especially the third, pair of prosomal limbs are enlarged and very
spiny. These limbs were presumably used for prey-capture, and analogies can be
drawn with the ‘catching basket’ formed by the spiny pedipalps of whip spiders
among the arachnids.”
“Our
knowledge of these bizarre animals is limited to only four species in two
genera described 80 years ago: Mixopterus kiaeri from
Norway, Mixopterus multispinosus from New York, Mixopterus
simonsoni from Estonia, and Lanarkopterus dolichoschelus from
Scotland.”
“All
are Silurian in age and come exclusively from the ancient continent of
Laurussia, which constrains our knowledge of the morphological diversity,
geographical distribution and evolutionary history of the group.”
Terropterus
xiushanensis represents the
first mixopterid from the ancient supercontinent of Gondwana as well as the
oldest known mixopterid.
Specimens
and reconstruction drawing of Terropterus xiushanensis: (a) appendages
II-VI, holotype; (b) reconstruction drawing of Terropterus xiushanensis,
dorsal and ventral views; (c) close-up of appendage V; (d) joint 5 or 6 of
appendage III, paratype; (e) joint 5 or 6 of appendage III, paratype; (f)
coxae, paratype; (g) genital operculum and the genital appendage, paratype.
Scale bars – 5 mm in (a), (d), (f), and (g); 2 mm in (e); 1 mm in (c). Image
credit: Wang et al., doi: 10.1016/j.scib.2021.07.019.
The
species was relatively large, reaching up to 1 m (3.3 feet) in length, and had
a ‘particularly enlarged prosomal limb III, characterized by a unique
arrangement of spines.’
It
likely played an important role of top predators in the Silurian marine
ecosystem when there were no large vertebrate competitors.
“The
paleogeographical distribution of mixopterids was rather limited until now and
no examples of this group have been previously discovered in Gondwana,” the
paleontologists said.
“Our
first Gondwanan mixopterid — along with other eurypterids from China and some
undescribed specimens — suggests an under-collecting bias in this group.”
“Future
work, especially in Asia, may reveal a more cosmopolitan distribution of
mixopterids and perhaps other groups of eurypterids.”
The study was published in the journal Science
Bulletin.
_____
Han
Wang et al. 2021. First mixopterid eurypterids (Arthropoda:
Chelicerata) from the Lower Silurian of South China. Science Bulletin 66
(22): 2277-2280; doi: 10.1016/j.scib.2021.07.019
Red dot indicates the current fossil discovery, and the yellow and orange dots indicate earlier fossil discoveries of a similar species. FIY, map is showing land mass positions during the Silurian period when these animals were alive.
Research
Area ‘a’ (some of the current fossils discovered here)
Research Area ‘b’ (some of the current fossils discovered here)
Published Research at: https://www.sciencedirect.com/science/article/pii/S2095927321005004