Lithomelissa Ehrenberg, 1847

Trubovitz, Sarah, Renaudie, Johan, Lazarus, David & Noble, Paula, 2022, Late Neogene Lophophaenidae (Nassellaria, Radiolaria) from the eastern equatorial Pacific, Zootaxa 5160 (1), pp. 1-158 : 39-41

Genus Lithomelissa Ehrenberg, 1847 , emend. O’Connor, 1997

Type species: Lithomelissa microptera Ehrenberg, 1854c

Description. A two-segmented lophophaenid that has an apical spine passing freely through the cephalis. Dorsal, ventral, and lateral spines protrude through the wall of the thorax, not forming ribs. Cephalis is large relative to the thorax, similar in proportion to Lophophaena and Peromelissa , but proportionally larger than it is in Ceratocyrtis . Thorax typically does not have a clear termination.

Remarks. Lithomelissa was first described rather vaguely, as a test with a single stricture, neither end lobate, and lateral wing-like spines ( Ehrenberg, 1847). This description could fit the majority of lophophaenid taxa. Initially, no species were described by Ehrenberg (1847 a), and no type species was designated for this genus. Thus, over the years there has been much confusion and disagreement in the literature regarding the definition of Lithomelissa . Haeckel (1881, 1887) understood a very broad concept of Lithomelissa , and split the genus into three subgenera: Acromelissa (with one horn), Micromelissa (with two horns), and Sethomelissa (with three or more horns). It appears that the species Haeckel placed in Acromelissa would best fit the modern usage of Lithomelissa (i.e., sensu Petrushevskaya, 1975 and O’Connor, 1997), but as many of Haeckel’s species were not illustrated, it is difficult to be certain of this. Several of the lithomelissids Haeckel assigned to subgenera Micromelissa and Sethomelissa have since been reassigned to Lophophaena (i.e., L. decacantha and L. buetschlii ). Bütschli (1882) described and illustrated several species of Lithomelissa (figs. 21–26), with all except for Lithomelissa haeckeli exhibiting a single apical horn passing freely through the cephalis (similar to those in Haeckel’s subgenus Acromelissa ). Jørgensen (1900, 1905) was also among the first to describe and illustrate the internal skeletal characteristics of Lithomelissa . But, confusingly, he abbreviated the dorsal spine as “A” and apical spine as “D,” and indicated that the apical spine runs along the side of the cephalis, rather than passing freely through it. This was certainly true of some species assigned to Lithomelissa at that time (i.e., Lithomelissa setosa Jørgensen , Lithomelissa thoracites Haeckel , Lithomelissa buetschlii Haeckel ), but did not represent many others, which have a free apical spine (i.e., Lithomelissa ehrenbergi Bütschli , Lithomelissa mitra Bütschli , and the species that would later be designated the type species of the genus: Lithomelissa microptera Ehrenberg ). Schröder (1914) reproduced Jørgensen’s illustrations and accepted his concept of the genus. Thus, by the early 1900s, there were at least two conflicting concepts of Lithomelissa and no designated type species.

Campbell (1954) designated the type species as Lithomelissa tartari Ehrenberg, 1854b , although this species had never been illustrated and was thus not a practical choice. Foreman (1968) remarked that any species assignments to Lithomelissa are “doubtful” due to the “inadequacy of the description of the type species.” For this reason, Petrushevskaya (1971) suggested the type species be considered Lithomelissa microptera Ehrenberg, 1854c by subsequent monotypy, as it had been adequately illustrated. However, unlike her predecessors, Petrushevskaya (1971) did not consider Lithomelissa to be Lophophaenidae , due to the apical horn passing through the cephalis rather than running along the side. Later, Petrushevskaya (1981) erected the subfamily Dimelissinae , and placed Lithomelissa into this group. To our knowledge, all other subsequent authors have considered Lithomelissa to be in Lophophaenidae , and we are of the same opinion because this genus is very similar to the lophophaenids Lophophaena and Peromelissa in every respect other than the position of the apical spine.

Petrushevskaya (1975) synonymized Lithomelissa with Acromelissa , and proposed that Lithomelissa microptera Ehrenberg be considered the type species of Acromelissa Haeckel, and that the name Lithomelissa should be discontinued because it does not have a reliable type species. However, since Acromelissa Haeckel is a junior synonym and subgenus of Lithomelissa Ehrenberg , Lithomelissa microptera Ehrenberg should actually be considered the type species of Lithomelissa Ehrenberg , and Acromelissa Haeckel should not be used. Lithomelissa microptera Ehrenberg was finally formally designated as the new type species of Lithomelissa by Petrushevskaya and Kozlova (1979), and adopted in most subsequent literature (e.g., Petrushevskaya, 1981, O’Connor, 1997), but not all (i.e., Nishimura, 1990). In her emendation of Lithomelissa, Nishimura (1990) considered the type species to be Lithomelissa tartari Ehrenberg, 1854b , and did not mention Petrushevskaya (1971, 1981). O’Connor (1997) provided the most recent and comprehensive revision of Lithomelissa , which considers the emendations of both Petrushevskaya (1971) and Nishimura (1990). This is the definition we follow here. O’Connor (1997) suggested that species lacking secondary left and right lateral bars, and with an apical spine not free within the cephalis should not be considered Lithomelissa , and should likely be reassigned to Lophophaena (including several open nomenclature taxa in Nishimura, 1990).

Here we observed the following species of Lithomelissa : Lithomelissa alkonost n. sp., Lithomelissa babai n. sp., Lithomelissa celsagula Renaudie and Lazarus, 2015 , Lithomelissa cheni Caulet, 1991 , Lithomelissa dybbuki n. sp., Lithomelissa ehrenbergi Bütschli, 1882 , Lithomelissa mitra Bütschli, 1882 , and Lithomelissa sirin n. sp. Here we do not include Lithomelissa capitata Popofsky, 1908 because it was transferred to Antarctissa by Petrushevskaya (1975). Lithomelissa jorgenseni Popofsky, 1908 is excluded here because the apical spine runs along the side of the cephalis and thus does not meet the criteria for the modern usage of Lithomelissa . We suspect this species may fit best in Botryopera given its similarities to Botryopera setosa ( Jørgensen, 1900) Kruglikova, 1989 , but as it was not observed during this study we do not attempt to make a formal transfer here. Upon examination of the author’s illustrations, Lithomelissa curta Kozlova, 1999 appears to be a trissocyclid rather than a lophophaenid, but it has not been officially transferred to our knowledge. We transfer Lithomelissa ? kozoi Renaudie and Lazarus, 2013a to Pelagomanes n. gen. in this manuscript (see below). Lithomelissa laticeps Jørgensen, 1905 was transferred to Lophophaena by Kurihara and Matsuoka (2010), and we agree because the apical spine runs alongside the wall of the cephalis is this species, excluding it from Lithomelissa . Lithomelissa setosa Jørgensen 1900 and Lithomelissa brevispicula Popofsky 1908 were both transferred to Botryopera by Kruglikova 1989 and Petrushevskaya 1986, respectively (see above). We transfer Lithomelissa spinosissima Tan and Tchang 1976 to Arachnocorys due to the position of the apical spine and nature of the thorax attachment (see above). Lithomelissa heros Campbell and Clark 1944 was moved to Botryometra by Petrushevskaya 1975; this species is clearly a cannobotryid. Lithomelissa hystrix Jørgensen, 1905 was included in Botryopera oceanica (Ehrenberg) group by Petrushevskaya (1975), as it does not meet the criteria for Lithomelissa . Lithomelissa robusta Campbell and Clark, 1944 was transferred to the spumellarian genus Lithelius by Foreman (1968), and appears to be a fragment of a litheliid although details are not clear in the original illustration. Lithomelissa amphora Stöhr 1880 is clearly a carpocaniid, and so is not included here. Lithomelissa haeckeli Bütschli 1882 is not included because the apical spine does not pass freely through the cephalis, and the strong feet are very unusual for lophophaenids in general. O’Connor (1997) suggested that this species be considered Lophophaena instead of Lithomelissa , but we do not believe this species belongs in either genus due to the overall shell shape and strong feet. It likely would fit better in a genus such as Cladoscenium , Clathromitra , Corythomelissa , or Pteroscenium , but it is outside the scope of our study to formally transfer it. We also exclude as nomina dubia: Lithomelissa tartari Ehrenberg, 1854b , Lithomelissa pycnoptera Haeckel, 1887 , and Lithomelissa microstoma Haeckel, 1887 . The latter two names so far as we know have never been used in subsequent literature, and may actually be nomina oblita.

Range.?Late Cretaceous –Recent.