Haikoucaris and allied
Dieter Waloßek at Mizzou1.Missouri.edu
Dieter Waloßek at Mizzou1.Missouri.edu
Wed Mar 9 10:12:31 CST 2005
Dear Ken and others,
Our paper appeared in 2004 and I have a PDF which I can send on demand.
Don't know what happened to Taylor & Francis, but I am sure one has to
pay for the PDF there anyway.
Actually, there is no need to re-write the arthropod evolutionary story
because Anomalocarididae sensu Hou & bergström, 1997, in the strict
sense do have appendages and are, therefore, Arthropoda, in our view
even Euarthropoda. The problem was just the bad conservation of these
often large and apparently soft forms, but Hou Xianguang, Bergström,
Jan & Ahlberg, Per 1995 described the limbs of, at least, one of the
taxa (Parapeytoia yunnanensis) quite well (though strangely placing the
forms into the Nemathelminthes). Accordingly, Anomalocarididae have a
set of head limbs – the antennulae and 2-3 postoral biramous limbs – as
well as trunk limbs with rigid basipodites bearing strong spines
medially, an endopod and a soft exopod (I can send pictures on demand).
The other problem is that some authors have put clearly unrelated stem
taxa and what-so-ever into the same basket anad named it
"anomalocaridids". This resulted in an undue and confusing mixture of
stem and euarthropod features (making them a paraphyletic assemblage).
We referred only to those taxa, which have been named Anomalicarididae
by Hou & Bergström in 1997. This excludes all stem arthopods like
Pambdelurion, Kerygmachela and Opabinia.
In our paper – and this will be even strengthened in an upcoming paper
on a new early representative of the Arthropoda s. str. in the journal
Arthropod Structure & Development (possbily 34,2) soon – we identified
the leg design of the antennula as plesiomorphic (and not a sensorial
type, as found in trilobites and a few other arthropod taxa). As
developed in Fuxianhuia protensa, Chengjiangocaris longiformis and the
new taxon Shankouia zhenghei, all from the Maotianshan-Shale biota in
China, Lower Cambrian, such an antennula is 15-segmented and (I use
this term to avoid confusion between a1 and a2, both given the name
antenna historically) seems to be modified into a grasping "organ" in
the stem lineage of Chelicerata.
Forms like Anomalocaris saron (about a hand long, pictures on demand),
exhibit this level – in our view. Amplectobelua symbrachiata has an
antennula with the same segments (also about 15), but carries, instead
of a regular series of spines, huge spines proximally and distally,
while the middle regions has only short spines. The distal region
bearing inwardly curved spines is virtually identical in both taxa
(pictures on demand).
In Parapeytoia yunnanensis, there are only four huge spines (sawed
marginally, picture on demand), and this holds true for all so-called
"great-appendage" arthropods (= one segment per spine and not a bundle
of spines as sometimes illustrated in papers).
Haikoucaris ercaiensis, newly described in our article, has an
antennula of 3 spines, and Chelicerata s. str. 2 left forming the
All these taxa share the two-divided peduncle portion, another
characteristic of this grasping organ antennula. A two-segmented
peduncle is even retained in a few pantopods.
Therefore, a characteristic of the cheliceratan lineage is the
predatory habit using the antennulae, the first appendages of the head,
as grasping devices. Hunting may have been different in the various
stem taxa because some have large, some have smaller eyes and some have
a long trunk with slim legs, while others have large exopods with long
setae possibly for swimming.
In further consequence we confirm the developmental and neurobiological
data that all antennulae whatever name and shape are homologous, i.e.
the chelicerae are just modified antennulae (as are the "great
appendages" or the first limbs of Anomalocarididae), even if one may
disagree with our other interpretations. And it also confirms that
Chelicerata are the sister group of the rest of Euarthropoda. A problem
now is with the trilobites that have sensorial antennulae subdivided
into many fine annuli. To us they cannot be regarded as closely related
to Chelicerata or even in-group. Their has to be reconsidered in the
future, not least since they have many more peculiarities not present
in other euarthropod taxa.
A segmented uniramous antennula and biramous post-oral limbs
(originally just a multi-annulated rod and a lateral flap) evolved only
once, i.e. in the stem species of Arthropoda s. str. – together with a
set of more features (Maas et al. 2004 and Waloszek et al. 2005 in
No need to develop them many times independently.
That's about all we propose in our discussion. Take a look.
Yours kindly, Dieter and Andreas
Chen Junyuan, Waloszek, D. & Maas, A. 2004:A new "great appendage"
arthropod from the Lower Cambrian of China and the Phylogeny of
Chelicerata. Lethaia37(1), 3-20.
Maas, A., Waloszek, D., Chen Junyuan, Braun, A.:, Wang Xiquiang & Huang
Diying 2004.Research on Early Phylogeny of Arthropoda. Progress in
Natural Science14(2), 158-166.
Waloszek, D., Chen J.-y., Maas, A. & Wang X.-g. in press 2005. Early
Cambrian Arthropods – New Insights into Arthropod Head and Structural
Evolution. Arthropod Structure & Development 34(2).
Dieter Waloszek and Andreas Maas
Section for Biosystematic Documentation
University of Ulm, Helmholtzstrasse 20, D-89081 Ulm, Germany
Tel. x49-(0)731-5031000, Fax x49-731-5031009
Biosystematic Information Service BIS:
Center of Orsten Research & Exploration C.O.R.E.:
email: dieter.waloszek at biologie.uni-ulm.de
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