A synthesis of the evolutionary history of erymoid lobsters (Crustacea, Decapoda, Erymoidea)

ABSTRACT A synthesis of our current knowledge of erymoid lobsters is presented. The superfamily Erymoidea includes two families, Erymidae Van Straelen, 1925 and Enoploclytiidae Devillez, Charbonnier & Barriel, 2019, together encompassing 81 species within six genera. Our examination of the palaeobiodiversity of this group and its evolution has revealed some variations through the Mesozoic with three important peaks, at the boundaries of: 1) Lower-Middle Jurassic; 2) Middle-Upper Jurassic; and 3) Lower-Upper Cretaceous. Whereas the origin of the first peak remains poorly known, the two others coincide with major modifications of the environment: the development of the European Jurassic carbonate platforms and the development of the European Chalk Sea and the partial flooding of North America during the mid- and Late Cretaceous. In addition to a notable peak of diversity, the Cretaceous is an important time interval in the evolutionary history of erymoids because the Early Cretaceous represented a long period of relatively low diversity and during the Late Cretaceous a strong decline of erymoid faunas is observed in Europe. However, the erymoids had already attained a worldwide distribution during the Early Cretaceous with occurrences in all oceans of the time. The analysis of the palaeobiogeographic distribution of these lobsters suggests the presence of important migratory paths, which probably favoured their spread and faunal exchanges between different areas across the globe.

These lobsters have been studied since the early nineteenth century. Indeed, the first descriptions of fossils, now considered to be erymoids, were produced by Mantell (1822Mantell ( , 1824Mantell ( , 1833, who studied the fauna found in the chalk formations of southern England, as well as by Desmarest (1817Desmarest ( , 1822, Schlotheim (1822) and Münster (1839), who recorded material from the Solnhofen Lithographic Limestones in southern Germany. Those authors described Astacus leachii Mantell, 1822 (type species of Enoploclytia M'Coy, 1849), Astacus sussexiensis Mantell, 1824 (type species of Palaeastacus Bell, 1850), and Macrourites modestiformis Schlotheim, 1822 (type species of Eryma Meyer, 1840). The palaeontological studies of Meyer (1840a, b), Quenstedt (1854) and Bell (1850) constituted a second wave, during which several erymoid species were erected, including Eryma ventrosum (Meyer, 1840b), which is typical of the Middle -Late Jurassic of western Europe. Later, at the beginning of the second half of the nineteenth century numerous extinct species of decapod crustaceans, including several erymoids, have been recorded on the basis of material from France, Germany and England, by Bell (1857Bell ( , 1863, Étallon (1857, 1859, 1861) and Oppel (1861Oppel ( , 1862. With the exception of the description of a small number of species by Trautschold (1866), Schlüter (1879) and Wright (1881), knowledge of erymoid faunas did not increase during the following twenty years. Important, yet mostly descriptive, contributions by Morière (1888), Sauvage (1891) and Lahusen (1894) appeared in print at the end of the nineteenth century. Following a study by Méchin (1901) on some crustacean fauna from the Lorraine region (eastern France), almost no work was done on erymoid lobsters at the start of the twentieth century. During the 1920s and early 1930s, our knowledge of European erymoid lobsters benefitted from important contributions by Van Straelen (1921, 1922, 1923, 1925, Beurlen (1928) and Woods (1930). Indeed, Van Straelen (1925) clearly recognised the intercalated plate as a diagnostic morphological feature of erymoids. Hence, he established the new family Erymidae to accommodate all lobsters that were characterised by the presence of such a plate. This family was accepted among subsequent workers, but its composition was strongly debated, as outlined in Devillez et al. (2019). The first important studies on extra-European crustacean faunas that included erymoid lobsters were those by Rathbun (1923Rathbun ( , 1926aRathbun ( , b, 1935 for North America and by Secrétan (1964) for Madagascar. Soon after, a major contribution by Förster (1966) came out; this was an extensive study that included a taxonomic review, phylogenetic considerations and a palaeobiological synthesis as well as observations on allometric growth and palaeoenvironmental considerations. Since then, a limited number of papers have appeared during the 1970s to 1990s (e.g . Feldmann 1979;Taylor 1979;Feldmann & McPherson 1980;Förster & Seyed-Emami 1982;Secrétan 1984;Garassino 1996).

MATERIAL AND METHODS
The overview of the palaeobiodiversity and palaeobiogeography presented here strongly relies on the most recent papers on erymoid lobsters. Indeed, Devillez et al. (2016 and Devillez & Charbonnier (2017, 2019, 2020 proposed an extensive review of these lobsters including novel descriptions of genera and most of the species, supported by an unambiguous use of characteristics of carapace groove pattern, the shape of P1 chelae, and the ornamentation of both carapace and P1 chelae. These studies were motivated by numerous uncertainties over the systematic and taxonomy of erymoid lobsters. For example, at the species level, Charbonnier et al. (2014) looked at the case of Eryma greppini Oppel, 1861, which was synonymised with Eryma bedeltum (Quenstedt, 1857) following Förster 's (1966) review. They identified a pair of dorsal domes in the former species that are missing in E. bedeltum and, on that evidence, concluded that E. greppini was a distinct species and questioned the validity of the synonymies established within the Erymidae by previous workers. Confusions also ruled at the genus level. Indeed, this persisted for a long time between Enoploclytia M'Coy, 1849 and Palaeastacus Bell, 1850. In this case, the confusion probably was the result of a combination of facts, revealed by the study of old literature sources. Originally, Mantell (1822) described Astacus leachii on the basis of heterogeneous material: P1 chelae with a globose propodus and long, slender fingers and other P1 chelae with short, wide fingers and adorned with strong spines. Considering these features, Mantell (1824) subdivided A. leachii in order to distinguish Astacus sussexiensis. M'Coy (1849) later established the genus Enoploclytia, and designated A. leachii as type species. However, the illustration supplied for the genus shows a carapace groove pattern, a morphology of the P1 chelae and an ornamentation that all correspond to that of A. sussexiensis. Moreover, A. sussexiensis was later designated type species of Palaeastacus by Glaessner (1929). Thus, the combination of these elements probably explains the confusion between these two genera, well illustrated in Glaessner (1969), who treated Palaeastacus as a subgenus of Enoploclytia, despite the strong differences between their carapace groove patterns.
We also note here that most of the erymoid records are from Europe, which means that this synthesis also reflects a strong bias in collection and literature records.
Finally, the present work uses the systematic framework recently proposed by Devillez et al. (2019)   era since the nineteenth century. However, the number of valid species has varied widely in subsequent studies. In the review proposed by Förster (1966), of the 139 species already described, less than 50% (i.e., 67 species) have been considered valid ones (Table 1). Indeed, some of the described species were wrongly assigned to erymoid genera or synonymized with other species. In the synthetic list of Schweitzer et al.
, which is not a taxonomic review, the number of species rose to 120, if only genera recognised to belong to the superfamily Erymoidea (see the systematics above), and their synonyms (Galicia Garassino & Krobicki, 2002, Protoclytiopsis Birshtein, 1958, as based on the most recent papers (Feldmann et al. 2015;Devillez et al. 2016Devillez et al. , 2017Devillez et al. , 2018Devillez et al. , 2019Devillez & Charbonnier 2017, 2019, 2020 are considered. We have noted that some of the species men-tioned, but not discussed in detail by Devillez et al. (2016) and Devillez et al. (2017) deserved careful re-examination. Devillez et al. (2016: 530) transferred Enoploclytia tenuidigitata Woods, 1957 (Aptian, Australia) to Palaeastacus on account of the typical groove pattern of carapaces assigned to that taxon. Further comparisons with the type material of Palaeastacus terraereginae (Etheridge Jr, 1914) (Barremian, Antarctica, Australia) have documented strong similarities between the two species. Indeed, both exhibit: 1) a closely similar groove pattern, with postcervical and branchiocardiac grooves becoming divergent towards their ventral termination; 2) a homogeneous ornamentation consisting of tubercles preceded by depressions; 3) both inflated ω and χ areas; and 4) P1 chelae with a short, rectangular and slightly globose propodus bearing straight and unusually fine fingers    (Garassino, 1996), from the Sinemurian of Osteno (Italy); F, specimen GPIT unregisteref of Eryma sp. from the Sinemurian of Ofterdingen (Germany); G, holotype MSNM i7606 of Palaeastacus meyeri (Garassino, 1996)  and globose P1 propodus with long and slender fingers. They also maintained Pustulina dawsoni (Woodward, 1900) (upper Campanian -lower Maastrichtian, Hornby Island, Canada) in Pustulina, however, but failed to mention any anatomical arguments in support of such an assignment. A careful examination of high-resolution pictures of the type specimens stored in the collections of the Geological Survey of Canada has now allowed their carapace groove pattern to be observed (Fig. 2); that of the holotype of E. minor is not preserved in its entirety: it has an elongated and bifurcated gastro-orbital groove, joined at mid-length of the cervical groove, and a sinuous postcervical groove with a short extension at carapace mid-height (Fig. 2B). The carapace groove pattern of P. dawsoni is almost complete. An elongated and bifurcated gastro-orbital groove is joined posteriorly at the mid-length of the cervical groove; the cervical groove is joined ventrally to a curved antennal groove; the postcervical groove is sinuous, with an extension at the level of carapace mid-height, and joined ventrally to a sinuous hepatic groove, joined anteriorly to the cervical groove; a short and isolated branchiocardiac groove is interrupted in the branchial region; a curved inferior groove is also joined to the posterior extremity of the hepatic groove. This specimen also has a rectangular P1 propodus bearing long fingers (Fig. 2F). This groove pattern and the morphology of P1 chelae of P. dawsoni are typical of Enoploclytia. Moreover, the type specimens of both E. minor and P. dawsoni have a very similar tuberculated ornamentation. These specimens also from localities on Hornby Island that are close in geography and stratigraphy. In conclusion, the morphological similarities as well as the geographic and stratigraphic arguments lead us to interpret P. dawsoni as a junior synonym of E. minor.
According to the present review, the number of valid species of Pustulina (11 species, rather than 12) remains stable, while that of Enoploclytia and Palaeastacus has almost been halved (10 species [versus 19] and 14 [versus 24]; Table 1). Eryma shows the strongest reduction in number of species that are considered valid by us. This number was divided by almost three between the listing by Schweitzer et al. (2010) and the most recent review (i.e., 24 versus 60 species). This reduction is due to: 1) the numerous species now identified as synonyms of others (e.g., Eryma ventrosum is an extreme case with 23 synonymised names recognised; Devillez & Charbonnier 2020); and 2) the species that have been reassigned to other genera, (e.g., Eryma foersteri Feldmann, 1979 is now regarded as a representative of Palaeastacus; Devillez & Charbonnier 2019). Stenodactylina is the sole genus to show an increase in the number of constituent species. This is due to reassignment of species earlier referred to Enoploclytia, Palaeastacus and, mainly, frotom Eryma. These changes result from a more detailed characterization of the genus that followed upon the publication of specimens with carapaces preserved in association with P1 chelae by Hyžný et al. (2015). Indeed, prior to that study, the genus Stenodactylina was known exclusively from a couple of isolated P1 chelae (Beurlen 1928;Schweigert 2013), so the carapace and its groove pattern remained unknown until 2015. All in all, Stenodactylina remains an uncommon genus, and Devillez et al. (2018) pointed out an important gap of almost 50 myr between the two Cretaceous occurrences of S. delphinensis (Moret, 1946) (Berriasian) and S. triglypta (Stenzel, 1945) (Coniacian).

Evolution of palaEobiodivErsity
The palaeobiodiversity of the Erymoidea can be analysed at different temporal (systems, series and stages) and taxonomic (family, genus and species) levels. In view of the fact that there is only a single species each on reccord from the Late Permian (Changhsingian; Fig. 3A) and the Paleocene (Fig. 3B, C), and because there are no records of Triassic erymoid lobsters, our discussion of erymoid palaeobiodiversity is restricted to Jurassic and Cretaceous occurrences. Moreover, in consideration of the relatively low number of known species and biases in collection and literature records, the elements given in our analysis proposed here should be only regarded merely as general trends.
More erymoid species have been recorded from the Jurassic strata (45 species) than from Cretaceous deposits (34 species). However, of those 45, ten species occur exclusively in Lagerstätten of Late Jurassic (Kimmeridgian-Tithonian). By removing the Lagerstätten effect, as discussed by Klompmaker et al. (2013), the Jurassic yields 35 species, a specific diversity that is very close to that of the Cretaceous (Fig. 4A, B). However, we have noted a marked change in the importance of the families Erymidae and Enoploclytiidae between the Jurassic and the Cretaceous. Indeed, the later family comprises fewer species during the entire Jurassic and an increase to almost half of the diversity of all Erymoidea during the Cretaceous.
At the generic level, Eryma (17 species) and Stenodactylina (17 species) are the most speciose during the Jurassic: they include 80% of the species known for this system. For the Cretaceous, Enoploclytia is the genus which comprises most species (nine), while the number of species of Palaeastacus remains stable (seven species in Jurassic and Cretaceous), and Pustulina is the sole genus to have an increased specific diversity compared to that of the Jurassic (four Jurassic species, seven Cretaceous ones). The number of species for other genera already recorded from the Jurassic is less important during the Cretaceous: 17 Jurassic species of Eryma and six for the Cretaceous, 17 Jurassic species of Stenodactylina and four for the Cretaceous.
Considering the stage-by-stage-evolution of erymid palaeobiodiversity, leaving out the taxa from Lagerstätten, three major peaks in specific diversity can be noted (Fig. 4C).
The first peak is seen at the boudary between the Lower and Middle Jurassic (Toarcian-Aalenian). This is strongly supported by the specific diversity of the genus Stenodactylina, which attains the highest number of species. This peak is followed by a reduction of 50% in species during the Bajocian. Subsequently, the specific diversity increases from the Bathonian to reach a second peak at the limit between Middle and Upper Jurassic (Callovian-Oxfordian). This coincides with the development of carbonate platforms across Europe, when Eryma reaches its maximum diversity. The Bathonian is also characterised by the rise of Eryma ventrosum, a common species in the Middle and Late Jurassic of western Europe, while there are no records anymore Eryma compressum (Eudes-Deslongchamps, 1842), which had been common since the Toarcian. A progressive reduction in the number of species starts during the Kimmeridgian-Tithonian. Indeed, from seven erymoid species on record from Oxfordian strata, the uppermost Jurassic has yielded only three reported species to date. This low specific diversity continues into the earliest of the Cretaceous, with only three reported species during the Berriasian, and characterises almost the entire Lower Cretaceous until the third peak at the boundary between the Lower and Upper Cretaceous (Albian-Cenomanian) is reached. However, contrary to the general trend, with five reported species, Pustulina reaches a higher specific diversity during the Early Cretaceous. The third peak coincides with the interval that witnesses the last occurrences of   Woods (1930), has also been noted from the uppermost Lower Jurassic of the United Kingdom (Förster 1966;Devillez & Charbonnier 2019). Considering the sheer number of palaeontological studies carried out across Europe since the nineteenth century, the bias in collection may be considered to be weak for this continent. It is then strongly speculative to assume that western Europe was a central spot from where erymoid lobsters spread out across the globe, since it is the only area from which the oldest Mesozoic representatives of the group have been reported. All Erymoidea recorded from the Middle Jurassic strata were found in the Northern Hemisphere, in Europe, northwestern North America and in northwestern and northeastern Africa (Fig. 6A). The only two enoploclytiids, Pustulina calloviensis (Förster, 1966) and Pustulina elegans (Förster, 1966), are known from western Europe, while erymids are widely distributed. Of Eryma compressum, in particular, the commonest species in Europe during the Middle Jurassic, there two southerly occurrences, in present-day Iran (Förster & Seyed-Emami 1982;Fig. 7B) and Morocco (Secrétan 1984). This suggests that this species spread to nearly the entire European part of the Tethys Ocean, the Central Atlantic margin (occurrence in the Bajocian), which had started to open up the onset of the Middle Jurassic (Scotese 2014c), and the North African margin in the southern Tethys Ocean (occurrence in the Aalenian). A recently reported specimen of E. compressum and Eryma ornatum (Fig. 6A), another well-known western European species, extends the geographical distribution of the genus to eastern Europe (Fanţescu et al. 2018, Metodiev et al. 2021. Some erymids have also been reported from northwestern North America, which was flooded during the Middle Jurassic: Stenodactylina walkerae (Feldmann & Haggart, 2008) (Fig. 8L) and Palaeastacus foersteri (Feldmann, 1979) (Fig. 8D). Their presence could have resulted from migrations of European populations. Indeed, both Stenodactylina and Palaeastacus had been present in western Europe since the Early Jurassic. Western Europe was also the closest region from where the northwest of North America via the Boreal Ocean could have been reached.
The geographic distribution of erymoid lobsters looks to have been wider during the Late than during the Mid-  Fig. 7A). This species, already known in western Europe during the Bathonian (Devillez & Charbonnier 2020), extends the distribution of Eryma further to the south than E. compressum seems to have done during the Middle Jurassic. The presence of E. ventrosum so far south during the Late Jurassic strongly suggests the existence of migrations of erymoid populations from western Europe to the Southern Hemisphere. Moreover, the presence of Stenodactylina in Madagascar during the Kimmeridgian-Tithonian could be a result of such migrations. This genus already occurred in western Europe and North America during the Middle Jurassic. However, the North American inlet was only connected to the Boreal Ocean only far in the north during the Middle Jurassic and only to the Pacific Ocean in the west during the Late Jurassic, so it was closed to the south.
In Lower Cretaceous strata, thirteen (out of 21) species were found in western Europe (Fig. 11A). The main difference with the Late Jurassic is that the number of enoploclytiids has strongly increased. Indeed, in Europe and North America there is almost the same number of species assigned to this family than that assigned to the Erymidae.
The presence of Eryma nippon Karasawa, Ohara & Kato, 2008 (Barremian, Japan;Fig. 7C) and Eryma moriedaorum Ando, Hirose, Ugai & Shimada, 2020 (Cenomanian, Japan) suggests the persistence of an erymoid fauna in the Far-East since at least the Kimmeridgian-Tithonian (Kato et al. 2010). In addition, important during the Early Cretaceous is the presence of erymoid faunas at the extreme south of the globe (Antarctica, Australia, Patagonia [Argentina]). The erymoids recorded from there exclusively belong to the Erymidae and constitute the first occurrences of these lobsters in Antarctica (Taylor 1979;Aguirre-Urreta 1989;Devillez et al. 2017), in Australia (Etheridge Jr 1914Woods 1957;Förster 1966;Devillez et al. 2017) andin Patagonia (Aguirre-Urreta &Ramos 1981;Aguirre-Urreta 1982. These occurences concern mainly the genus Palaeastacus (Fig. 12). Some specimens from the Aptian of Patagonia were assigned to Palaeastacus sussexiensis (Mantell, 1824) by Aguirre-Urreta (1989: fig. 8). This assignment was accepted by Devillez et al. (2016Devillez et al. ( , 2017. However, these specimens exhibit some differences with P. sussexiensis: the P1 propodus is rounded in shape, the basis of the dactylus is relatively thin, the carapace ornamentation is fine and lacks strong spines in the cephalic and cardiac regions, and there are no rows of strong spines on the dorsal surface of P1 propodus. The shape of the P1 chelae and the dense, fine ornamentation of the carapace and P1 chelae of the Patagonian specimens are closely similar to those of Palaeastacus terraereginae (Etheridge Jr, 1914), a species recorded from the Barremian of Antarctica, Australia and Patagonia and from the Aptian of Queensland (Australia). Therefore, the Patagonian specimens recorded by Aguirre-Urreta (1989) are here considered to be conspecific with P. terraereginae. Thus, among the erymoids of the extreme south of the globe, P. terraereginae was widespread in this area of the world during the late Early Cretaceous. Devillez et al. (2016) described an exceptional fauna from southeastern France. During the Early Cretaceous, this northeast oriented area of almost 350 × 300 km provided eight species assigned to five (out of six) erymoid genera currently known: Eryma vocontii Devillez, Charbonnier, Hyžný & Leroy, 2016, Eryma glaessneri (Van Straelen, 1936, Palaeastacus loryi (Van Straelen, 1923), Pustulina colossea Devillez, Charbonnier, Hyžný & Leroy, 2016, Pustulina occitana Devillez, Charbonnier, Hyžný & Leroy, 2016, Pustulina victori Devillez, Charbonnier, Hyžný & Leroy, 2016, Stenodactylina delphinensis (Moret, 1946, and Tethysastacus tithonius Devillez, Charbonnier, Hyžný & Leroy, 2016 (Fig. 13). With eight species (of 21) on record, this area of limited extent is known to have yielded: 1) the most diverse erymoid fauna of the Lower Cretaceous; 2) the most diverse Pustulina assemblage; and 3) the two sole fossils of Tethysastacus currently known (holotype MNHN.F.J03351 of T. tithonius and cast MNHN.F.A70286 of another specimen from an unknown locality).
The only erymoid fauna known from the Southern Hemisphere during the Late Cretaceous (Fig. 11B) has been described from the Campanian of Madagascar (Secrétan 1964;Charbonnier et al. 2012a;Devillez et al. 2017;Fig. 9). Secrétan (1964) noted the affinities between erymoid faunas from Madagascar and Australia (Figs 1; 12), Europe and North America (Fig. 8) and deduced from this the existence of migratory paths that allowed exchanges between Madagascar and other continents. An isolated P1 chela from the Santonian of France assigned to Stenodactylina cf. armata (see Devillez et al. 2017;Fig. 14K) confirms the probable exchange of faunas between Europe and Madagascar.
We have noted a spectacular change in erymoid distribution in the Upper Cretaceous. A shift of the pole of diversity from Europe to North America with the addition of an apparent reduction of specific diversity (21 species in the Lower Cretaceous, 15 in Upper Cretaceous). The flooding of the southern USA and northeastern Mexico since the Early Cretaceous (Scotese 2014a, b) could provided new environments favourable for the settlement and diversification of an erymoid fauna. In contrast, the development and relative stability of the western European Chalk Sea possibly did not provide enough changes in environmental conditions to enable a strong diversification and modification of the erymoid fauna (Fig. 14). Indeed, this stability could have allowed the persistence of well-adapted species -in this case, Enoploclytia leachii and Palaeastacus sussexiensis -without competitve pressure of too many immigrant forms. Devillez et al. (2017) discussed in detail the absence of erymoids in North America between the Oxfordian and the Albian. They proposed two hypotheses to explain this 50 myr hiatus: 1) a bias in collection or literature records; or 2) a genuine absence of erymoid lobsters in North America. As to the second hypothesis, the authors emphasised that the Cretaceous fauna in the Gulf of Mexico could have resulted from immigrations of populations from Eurasia. Indeed, the proximity of this continent at the end of the Early Creta- ceous, the potential access in the North through the Boreal Sea and the presence of all genera recorded from the Lower Cretaceous (i.e., Enoploclytia, Palaeastacus and Stenodactylina) provide strong support for this scenario. They also pointed out the absence of occurrences of erymoid lobsters in the Western Interior Seaway (WIS), which connected the Boreal Ocean in the north with the Atlantic Ocean in the south during almost the entire Late Cretaceous (Gill & Cobban 1966, 1973Molenaar & Rice 1988;Eicher & Diner 1989;Scotese 2014a, b). Five erymoid species were recorded from Texas, at the southern extremity of the WIS. In view of the fact that the connection between the WIS and the Atlantic had no clear geographical boundary and remained relatively stable, Devillez et al. (2017) suggested that the apparent absence of erymoids in the WIS could have resulted from a bias in collection or literature records.
palEogEnE Enoploclytia gardnerae (Rathbun, 1935), the sole erymoid species to have been recorded from the Cenozoic, is from the Paleocene of Alabama (southern United States; Rathbun 1935) and northern Mexico (Vega et al. 2007;Martínez-Díaz et al. 2017;Fig. 3B, C). Thus, as far as we are aware, the last known erymoid populations lived in the Gulf of Mexico.

CONCLUSIONS
The present synthesis supplies a general overview of current knowledge of erymoid lobsters, for which 81 valid species within six genera are currently known. During their almost 190 myrlong evolutionary history, their palaeobiodiversity fluctuated with three periods of higher specific diversity at the boundaries of the: 1) Lower-Middle Jurassic; 2) Middle-Upper Jurassic; and 3) Lower-Upper Cretaceous. The second and third peaks could have been linked to important palaeoenvironmental changes: the development of carbonate platforms across Europe and the development of the European Chalk Sea in addition to the flooding of vast North American territories, respectively.
During their long history, erymoids colonised the shelves around each continent. Such a colonisation may have been possible through some migratory paths, which seem to have had a Eurasian origin. However, in consideration of the smaller number of data for the Southern Hemisphere, this interpretation could reflect a collection/recording bias. Nevertheless, the fossil record does indicate that erymoid lobsters have already attained their worldwide distribution by the Early Cretaceous.
Despite the survival of these crustaceans through the three last "biological crises", the reasons that led to the extinction of the erymoid lobsters during the Paleogene cannot be identified as yet.Our study of erymoid palaeobiodiversity points out a decline of the group since the beginning of the Late Cretaceous, especially in Europe. New data on the relationships between erymoid lobsters and other groups of decapod crustaceans, such as the nephropid lobsters, for which the diversity seems to increase during the Cretaceous, may yield additional data allowing us to explain the demise of erymoids.
The clear definition of erymoid genera and the consistent application of the taxonomic criteria, as provided in the most recent papers, have brought to light numerous cases of synonymy and erroneous assignments. In short, the case of the erymoid lobsters is a very good example of the great importance of taxonomic reviews in order to provide useful data in the studies of past biodiversity study and of evolution at different systematic and geographic scales.