In 1997, two months apart, Pierre Morzadec (Morzadec 1997), and Bruce Lieberman and Gerald Kloc (Lieberman & Kloc 1997) published different revisions of the trilobite originally described as Asteropyge mesocristata (LE MAÎTRE 1952), an Upper Emsian asteropygine known in Morocco and Algeria. Morzadec's work dealt with a broad revision of the Devonian Asteropyginae of the Ougarta (Algeria) and he created the genus Hollardops with the Le Maître specimen as holotype, noting that Hollardops is a unique asteropygine because it has only 10 thoracic segments (all other asteropygine taxa bearing 11 segments). Shortly after, Lieberman & Kloc's analysis of various Asteropyginae based on cladistic analysis, evolutionary and biogeographic patterns included the description of two species from Morocco. Unware of the Morzadec paper, they named these : Philipsmithiana burtandmimiae and Philipsmithiana hyfinkeli. Since Dr Morzadec's publication preceeded Lieberman & Kloc's work, the genus name Hollardops MORZADEC 1997 has priority over Philipsmithiana which is relegated to a junior subjective synonym (see Morzadec 2001, Jell & Adrain 2003).

Morzadec noted that Dorothée Le Maître based her 1952 description of Asteropyge mesocristata on a juvenile specimen with a cephalon only 6 mm long and with an eye having 27 dorso-ventral files and a maximum of 6 lenses per file. He then indicated that adult specimens of H. mesocristata have eyes with 29 dorso-ventral files, and a maximum of 9 lenses per file, but does not give a count of pygidial axial rings of mature specimens. He also described H. lemaitreae, found in Algeria. Lieberman & Kloc (1997) described "Philipsmithiana hyfinkeli" as having eyes with a maximum of 9 lenses per dorso-ventral file, and a pygidial axis with 15 rings. "Philipsmithiana burtandmimiae" was described as having eyes with a maximum of 7 lenses per dorso-ventral file, but they did not give a specific pygidial axis ring count for "P. burtandmimiae". Because they listed 15 or 16 rings for the genus, and since P. hyfinkeli was described as having 15 rings, one can suppose that by elimination, some "P. burtandmimiae" must have 16. Altogether Lieberman & Kloc (1997) described 17 features with differences between the two species. Many of the differences were based on measurements inadequately described, so they are difficult to verify. A close examination of the photos in the paper shows that many of the reported differences are not distinct and do not appear to be consistent across all the specimens shown for a given species. The paper also contains a glaring error, in that it says "P. hyfinkeli" has a thorax with 11 segments.

In 2001, P. Morzadec published a paper on Moroccan Asteropyginae in which he explained that Lieberman & Kloc's "Philipsmithiana hyfinkeli" is synonymous with "Hollardops mesocristata". The descriptions of the two species are similar enough that this conclusion seems acceptable. He also described H. mesocristata as very common and that H. burtandmimiae could be distinguished from H. mesocristata "by the anterior part of cephalon being less round, a larger visual surface with 27 dorso-ventral files with a maximum of 8 and exceptionally up to 11 lenses per file, a higher number of axial rings (15-16) in the pygidium which is longer, with pygidial spines longer and more acute, and a shorter median spine." In his discussion of H. burtandmimiae , Morzadec stated that this species has a larger eye [than H. mesocristata] with up to 11 lenses per file, while Lieberman & Kloc's description said it had a smaller eye with a maximum of 7 lenses per file. Morzadec counted a higher number of pygidial axial rings (15-16) for H. burtandmimiae, while Lieberman & Kloc 1997 specified 15 for "P. hyfinkeli" and (presumeably) 16 for "P. burtandmimiae".

The inconsistencies and ambiguities are not easily reconciled. An examination of a longer series of specimens of Hollardops shows that large specimens of what might be called H. mesocristata by most diagnostic characteristics can have up to 11 lenses per file, and it may well be the case that both species can have up to 11 lenses per file in larger specimens. Also, most adult specimens seem to have fewer than 15 axial rings. So it seems that these two features tend to be rather variable depending on the maturity of the individual. We conclude that counting lenses and axial rings alone is insufficient to distinguish these species, and it raises doubts that separate species exist at all. Given the small differences in features, it may well be that the two described species represent extremes of a continuum of variation, explaining the current difficulties anyone faces identifying well-prepared moroccan Hollardops specimens.

The aim of this study is to examine a statistically significant sample of complete and well-prepared specimens of Moroccan Hollardops from worldwide collections, via clear, dorsal digital images. We will collect accurate locality and morphological character data on these specimens and compare them critically with the descriptions presented in the literature. Statistical analyses will be made on morphological data to describe range and variation, and the hypothesis that two distinct morphological species exist will be tested against a null hypothesis that one variable taxon with no significant bimodality of characters exists.

References :

JELL P.A. & ADRAIN J.M. 2003. Available generic names for Trilobites. Memoirs of the Queensland Museum 48 (2) : pp. 331 - 553.

LE MAÎTRE, Dorothée. 1952. La Faune du Devonien inférieur et moyen de la Saoura et des Abords de l'Erg el Djemel (Sud-Oranais). Bulletin Service Carte géologique de l'Algerie (1, Paleontologie) 12 : pp. 1 - 171.

LIEBERMAN, Bruce S. & KLOC, Gerald. 1997. Evolutionary Biogeographic Patterns in the Asteropyginae (Trilobita, Devonian) Delo, 1935. Am.Mus.Nat.Hist. Bull. 232 .

MORZADEC, Pierre. 1997. Les Trilobites Asteropyginae du Dévonien de l'Ougarta (Algérie). [Asteropyginae Trilobites from the Devonian of the Ougarta (Algeria).] Palaeontographica Abt.A 244 : pp. 143 - 158.

MORZADEC, Pierre. 2001. Les Trilobites Asteropyginae du Dévonien de l'Anti-Atlas (Maroc). [Asteropyginae Trilobites from the Devonian of the Anti-Atlas (Morocco)]. Palaeontographica Abt.A 262 : pp. 53 - 85.