Contributions to Zoology, 72 (2-3) 169-172 (2003)
SPB Academic Publishing bv, The Hague
Fossils and decapod phylogeny
Frederick+R. Schram & Christopher Dixon
Institute for Biodiversity and Ecosystem Dynamics, University ofAmsterdam, Mauritskade 57, NL-1092 AD
Amsterdam, the Netherlands
Keywords:: Decapoda, phylogeny, cladistics
Abstract closely related as Meiura. The analysis of Scholtz
& Richter was based on the manual Method of
for An expanded series ofmorphological characters developed Hennig, but Schram (2000, 2001) undertook a com-
a cladistic analysis ofextant decapods has yielded a new hypo- puter-based cladistic study, which essentially con- for the ofthe this data- thesis phylogeny group. Application of firmed their results. selected fossil base to genera produces some interesting results Nevertheless, some differences occurred in and and demonstrates the feasibility of treating fossils as full
in of Schram’s tree. Enoplometopus emerged separate equal partners the study decapod phylogeneticrelationships.
In addition, it seems clear that rigorous cladistic methods can from the other clawed lobsters; Astacida was sepa-
be used evaluate the of rather to phylogenetic positions fossils, rate from all the other fractostemalians; and Neogly- than ad hoc speculation. phea (the only living memberof the Glypheoidea),
although previously classified with the achelates,
emerged within the higher fractosterns. The con- Introduction sensus values within the paraphyletic “lobsteroids”,
however, remained low. Our understanding of the phylogeny of the deca- A more comprehensive examination of decapod is in pod crustaceans a true work progress. Although morphology was undertaken with additional taxa the Bur- matter was thought settled for many years, and characters by Dixon et al. (in press) and a new kenroad (1963, 1981) reopened debate on the arrangement of higher taxa arose (Fig. 1). The frac-
subject. Some consensus about the relationships tostern clade disappeared and the characteristic the lower around amongst decapods quickly emerged ofthat features group were suggested to be a mani- a paraphyletic of natantians, but most arrangement festation of burrowing life styles. In its place, the
efforts were based on morphology Schram, (see old Astacidea (now including the glypheoids, and
2001, for a However, Scholtz & Rich- summary). subsuming Enoplometopus back into Homarida) re-
ter (1995) undertooka new analysis based on exami- emerged alongside a new clade, the Sterropoda.
nationof that focused on the morphology Reptantia Within the latter group, the Thalassinida occur along
and a new scheme for these proposed phylogenetic with the Eurusternalia, a new grouping of achelates
forms. They found polychelids to be a sister The group with meiurans. branching arrangements of this to Eureptantia, within which the achelate forms were remain stable under various alterna- new tree very
a sister clade the Macrochelata. Within the lat- to tive options, and moreover present another posi-
ter, the old Astacidea was broken up to separate tive result. The trees of Scholtz & Richter (1995)
the clawed lobsters from the Fracto- a new group, and Schram (2001) are unbalanced, presenting es-
sternalia. While there was uncertainty concerning sentially a phylogenetic comb of sequentially ar- the relationship of the fractostern crayfish and the ranged clades. The Dixon et al. tree is much more
thalassinideans, the Anomala and Brachyura were balanced, at least with regard to the Reptantia.
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Fig. L Simplified cladogram from Dixon et al. (in press) ofmajor relationships within Decapoda.
The Dixon al. undertaken for two examined a selected of et project was we array well-preserved reasons. First, we wished to establish a morpho- replant forms from the fossil collections of the logical baseline for decapod phylogeny that could Teylers Museum (Haarlem). These included the be further and tested with both the of Jurassic Solnhofen explored use genera Eryma, Eryon, Glyphea, molecular and additional and which also added sequence data, expansion Mecochirus, to we scoring of the taxon sample. That project continues in col- for the earliest decapod fossil, the Devonian lob- laboration with our colleague Dr Shane Ahyong. ster Palaeopalaemon newberryi (cf. Schram et ah,
added Second, we wanted to provide a starting point upon 1978). Taxa were individually and as a whole which the of extinct fossil the matrix to their individual and phylogenetic position to assess group
be the forms could assessed. This paper is a progress effect on resulting tree. report of that second project. The results (Fig. 2) confirm the tree ofDixon et
al. (in press). Furthermore, the lack of information
about some features in the fossils at hand did not
result in of of The analysis collapse any many branching points
the master analysis. The two fossil glypheoid gen-
studied with The data set of Dixon et al. contains 70 characters, era we grouped the extant Neoglyphea
form Asta- of which 52 are multistate. Of these, 60 characters and these together a sister group to the
cidea. is within the clawed were retained for this study based on the likeli- Eryma placed lobsters
could the sister taxon to and hood that they be found on well-preserved as Enoplometopus. Eryon fossils. Interestingly, the reduced database repli- the polychelids do not form a monophyletic group cated the but basal tree obtained from the full database, con- as previously thought, Eryon is instead
the the The result firming stability of the new tree. In addition, to Eureptantia. most surprising
Downloaded from Brill.com10/01/2021 08:19:56AM via free access Contributions to Zoology, 72 (2-3) - 2003 171
2. fossil and extant Pig. Cladogram of relationships among genera of replant decapods
Was the placement of Palaeopalaemon, the earliest assessments ofphylogenetic relationships and Jenner
known the unresolved Inclusion of fossils is thus decapod, high in tree at an (2002). a necessary com-
with the Thalassinida and the of studies. Polytomy Euruster- ponent any phylogenetic Nevertheless,
nalia. fossils afford distinct problems mainly related to
It seems clear from these preliminary results that missing data (Schram, 1991; Schram& Hof, 1998). the evaluation of fossils directly in connection with Generally, one cannot overload an analysis with
modern taxa to obtain a more comprehensive as- fossils without destabilizing the branching array of
sessment of decapod phylogeny is feasible. a tree. The missing data tends to inject too much
Any phylogenetic tree is only as good as the data uncertainty into the processing of data by the cur- that are included in the analysis. The resultant pat- rent algorithms. Thus it is encouraging to have a
tern a of characters that character for that applies only to specific set set decapod crustaceans can pro-
have been scored for a of taxa. Jenner duce stable and reasonable specific array trees provide assess- & Schram (1999) demonstrated the need for the ments concerning the phylogenetic affinities of
ni °st comprehensive analyses possible in regard to fossilized forms. both character and taxon sets to obtain accurate The results obtained here for a selected set of
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Jenncr R. 2002. Boolean and character taxa must be built upon. While it is reassuring to logic state identity:
pitfalls ofcharacter coding in metazoan cladistics. Contrib. see that fossil decapod taxa are appearing in rea- Zool. 71: 67-91. sonable places on the tree, we nonetheless cannot Jenner Schram FR. 1999. The of R, grand game metazoan be complacent about past assumptions concerning phylogeny: rules and strategies. Biol. Rev. Cambr. Phil. the relationships among fossil and living decapods. Soc. 74: 121-142.
Scholtz G, Richter S. 1995. Phylogenetic systematics ofthe
reptantian Decapoda (Crustacea, Malacostraca). Zool. Jour.
Linn. Soc. 113: 289-328. Acknowledgements Schram FR. 1991. Cladistic analysis of metazoan phyla and
the of 35-46. In: Si- placement fossil problematica, pp.
We wish to special thanks to Dr Shane Ahyong for his express monetta A, Conway Morris S (eds). The Early Evolution
into our database of characters. Pro- continuing input evolving of Metazoa and the Significance of Problematic Taxa fessors Gerhard Scholtz and Rod Feldmann, and Dr Stefan Richter Cambridge: Cambridge University Press. have provided valuable insights and to further the of suggestions Schram FR. 2000. Phylogeny decapods. Studi e Ricerche, project along. Assoc. Amici Mus. civ. ‘G. ZannatoMontecchio Maggiore:
61.
Schram FR. 2001. Phylogeny of decapods: moving towards
a consensus. Hydrobiologia 449: 1-20. References
Schram FR, Feldniann RM, Copeland MJ. 1978. The late
Devonian Palaeopalaemonidae and the earliest decapod Burkenroad MD. 1963. The Evolution of the Eucarida crustaceans. Jour. Paleo. 52: 1375-1387. (Crustacea, Eumalacostraca), in Relation to the Fossil Schram FR, Hof CHJ. 1998. Fossil taxa and the relation- Record. Tulane Stud. Geol. 2: 1-17. of 273-302. ships major crustacean groups, pp. In: Edge- Riirkcnroad Ml). 1981. The Higher Taxonomy and Evolu- combe G (ed.). Arthropod Fossils and Phylogeny. New tion of Decapoda (Crustacea). Trans. San Diego Soc. Nat. York: Columbia University Press. Hist. 19: 251-268.
Dixon CJ, Ahyong ST, Schrani FR. in press. A new hy- Received 31 March 2003 pothesis of decapodphylogeny (Crustacea: Malacostraca).
Crustaceana
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