Erik Norman Kjellesvig-Waering

“ Diagnosis.—Ventral shield and metastoma unknown; eyes located in posterior half of carapace, opisthosoma undifferentiated, trilobation present; last two legs very long.
The above family diagnosis is based on the type species of Stylonurus as restricted here. However, if genera such as Stylonuroides, Stylonurella, Parastylonurus, Brachyopterus and Brachyopterella are used in the diagnosis, then a much better and more complete diagnosis can be made. I suspect, however, that some of these genera will be found eventually to have no significant affinities with the type genus. ”

“ Remarks.—The Pageidae differ from the other families that retain an epistoma, namely the Stylonuridae and Laurieipteridae, in the coffin-shaped metastoma, as against the long, deeply-notched metastoma of the Stylonuridae, and the broadly subrectangular one in the Laurieipteridae. The trilobation, although considered here a generic character, may well be of higher taxonomic importance. The family is monotypic at present. ”

“ If the genus Stylonurus is to date from 1856 when Page first proposed it with S. powriensis as obvious type species by monotypy, then the original name of the species must be used, since the genus could not have been proposed without a type species. The nearly whole specimen came from the Lower Devonian Old Red Sandstone of Scotland, and revealed long, slender legs without the characteristic paddles which characterized the hitherto known eurypterids. ”

“ Descriptions of all families and genera of the Stylonuracea are included here, as well as lists of the species referred to each genus. The families included are: Dolichopteridae, Stylonuridae, Pageidae, Drepanopteridae, Kokomopteridae, Rhenopteridae, Laurieipteridae, Woodwardopteridae, and Hibbertopteridae. ”

“ Genus Parastylonurus, new genus
Diagnosis.—Stylonuridae of small to medium size; prosoma rounded-quadrate; wider than long, with lateral eyes, arcuate and located on anterior half of the carapace; metastoma very long, with deep triangular notch or deeply cordate and with base truncated; first three walking legs very short with single opposable spines on each joint; last two walking legs very long, reaching to the last tergite; podomere-count: ?–?–7?–8–9–9; ornamentation consists of scales; opisthosoma narrow, undifferentiated ”

“ Remarks.—This genus of gigantic eurypterids is composed of two famous species, Hallipterus excelsior (Hall) of New York and H. lacoanus (Claypole) of Pennsylvania, and is well known through the famous restorations of Beecher, and later of Clarke and Ruedemann. Unfortunately, these well known restorations, except for the carapace and first legs, were based mainly on the opisthosoma and appendages of other Stylonuracea. Differences between this genus and Laurieipterus or Ctenopterus have been discussed under the Remarks on those genera. ”

“ The most interesting feature is the shape of the metastoma, which is roughly oval, with a narrow notch at the anterior and a broad base which is slightly cordate or emarginate (see fig. 98) . It measures 8.1 mm. in length and 7.2 mm. in greatest width (see fig. 95) . The female, or Type B (see fig. 97) , operculum is well preserved, showing even such details as the setae. The appendage is small, about one-third the length of the operculum, and consists of an undivided, rather broad lanceolate joint, with two triangular joints at the distal end. ”

“ It is, as the species name of the genotype indicates, and as Størmer (1934, p. 103) has pointed out, another link between the Dolichopteridae and the Stylonuridae, a further step in the transition from species such as Ruedemannipterus stylonuroides (Clarke and Ruedemann) . However, the long carapace and reniform eyes, a considerable departure from the usual greatly arcuate eyes of the stylonurids, may well reveal some affinities with the family Rhenopteridae. ”

“ The following species are recognized for this genus:
Genus Strobilopterus Ruedemann, 1935
Diagnosis.—Dolichopteridae of medium size; test covered with pustules and semi-lunar scales; prosoma semiovate; compound eyes submarginal; ocelli unknown; ventral doublure unknown; sixth appendages with movable, supplementary flat lobes on distal joints, ultimate joint forming large, flat lobe; distal joints and lobes forming paddle with strongly serrate margin; metastoma very narrow, cordate at anterior end; base unknown; male median appendage very long, consisting of one undivided joint ”

“ Nevertheless, the flattened podomeres indicate that if Tarsopterella is a stylonuracean, it should probably be referred to the Dolichopteridae. This is done here with considerable misgivings until the ventral side is known or some more prosomal appendages are found of this highly spectacular eurypterid. It is not precluded that Tarsopterella may not belong among the Eurypteracea. ”

“ The family is considered to include two genera, Borchgrevinkium and Woodwardopterus.
Genus Borchgrevinkium Novojilov, 1959
Diagnosis.—Carapace elongated-parabolic; eyes unknown; legs mainly unknown, except basal (?) joints, which are highly spinous, undifferentiated; mesosoma with first two tergites longer than the rest of the mesosomal tergites; opisthosoma undifferentiated, with trilobation, caused by two ridges, present from the third to the tenth tergites ”

“ Genus Drepanopterus Laurie, 1892
Diagnosis.—Drepanopteridae of small size; prosoma horseshoe shaped, narrower at base than at the rounded lateral margins; wide marginal rim; eyes arcuate, located at midsection; prosomal appendages stout, increasing gradually in length posteriorly and devoid of spines except for possible spurs (?) on the ends of central joints of the posterior (VI) leg; this leg (VI) terminates in a flattened, slightly expanded, falcate joint, and reaches only to the anterior part of the postabdomen; metastoma ovoid and cordate at the anterior end ”

“ The specimen is shiny, fairly dark brown; but curiously it reveals a narrow, very dark brown line, over one millimeter wide, that runs through the center of the dorsal length of the opisthosoma. This is not to be mistaken for a suture as it is definitely a color distinction. This is the first instance of a purely colored ornamentational pattern known in the stylonuroids. The dorsal side is covered with scales, most of which are semi-lunar in shape; others become rather pointed. The doublures of the tergites are heavily hirsute. ”

“ The mid-line represents the transverse suture. There were no deltoid plates developed. The inner part of the opercular plates and the median organ were covered with setae.
is entirely undifferentiated. In the latter the tergites of the metasoma are very wide and conical and almost grade into the wide (anteriorly) , wedge-shaped or clavate telson. A very important difference lies in the presence of spines in the fourth walking leg of Kokomopterus as compared to the non-spinous character of the same leg in Drepanopterus. ”