BACKGROUND: IGTS is a rare phenomenon of paradoxical germ cell tumor (GCT) growth during or following treatment despite normalization of tumor markers. We sought to evaluate the frequency, clinical characteristics and outcome of IGTS in patients in 21 North-American and Australian institutions. METHODS: Patients with IGTS diagnosed from 2000-2017 were retrospectively evaluated. RESULTS: Out of 739 GCT diagnoses, IGTS was identified in 33 patients (4.5%). IGTS occurred in 9/191 (4.7%) mixed-malignant GCTs, 4/22 (18.2%) immature teratomas (ITs), 3/472 (0.6%) germinomas/germinomas with mature teratoma, and in 17 secreting non-biopsied tumours. Median age at GCT diagnosis was 10.9 years (range 1.8-19.4). Male gender (84%) and pineal location (88%) predominated. Of 27 patients with elevated markers, median serum AFP and Beta-HCG were 70 ng/mL (range 9.2-932) and 44 IU/L (range 4.2-493), respectively. IGTS occurred at a median time of 2 months (range 0.5-32) from diagnosis, during chemotherapy in 85%, radiation in 3%, and after treatment completion in 12%. Surgical resection was attempted in all, leading to gross total resection in 76%. Most patients (79%) resumed GCT chemotherapy/radiation after surgery. At a median follow-up of 5.3 years (range 0.3-12), all but 2 patients are alive (1 succumbed to progressive disease, 1 to malignant transformation of GCT). CONCLUSION: IGTS occurred in less than 5% of patients with GCT and most commonly after initiation of chemotherapy. IGTS was more common in patients with IT-only on biopsy than with mixed-malignant GCT. Surgical resection is a principal treatment modality. Survival outcomes for patients who developed IGTS are favourable.

Arthrophycus alleghaniensis is a well-known trace fossil common in the lower Silurian of the Appalachian Basin, eastern U.S.A. Despite the distinctive morphology of this trace, with few exceptions, hypotheses about the nature of the tracemaker have not extended beyond that of a long-bodied, segmented organism. A single organic compression of a long-bodied arthropod discovered in shale interbedded with sandstones containing A. alleghaniensis in the Silurian (Llandovery) Tuscarora Formation at Mann Narrows, Pennsylvania is described. The specimen preserves evidence of two trunk tagmata: an anterior tagma with tergites extending into broad, rectangular pleurae, and a posterior tagma bearing long, curved spines. Head and appendages are not preserved. The new arthropod, Pleuralata spinosa n. gen. n. sp., matches the size and general morphology required for an A. alleghaniensis tracemaker. Precise systematic affinities of this new arthropod could not be determined. This discovery supports the conclusion that the tracemakers of various Arthrophycus ichnospecies are likely poorly preserved, and presently unknown, members of the Ecdysozoa.

Upper Silurian and lowermost Devonian fossil plant assemblages are often dominated by fragmentary remains of problematic land plants that are composed of a tubular anatomy. Traditionally, these remains have been divided into two morphotypes: large three-dimensionally preserved axes (the Prototaxites group), and smaller thalloid incrustations referred to the genus Nematothallus Lang. Because of their peculiar anatomy of different combinations of tubular elements, these plants do not appear to be closely related to the Tracheidatae (sensu Bremer et al., 1987). Neither do they fit easily into any extant algal groups (Rossat, 1952; Edwards, 1982; Strother, 1988). For these reasons, when he first described the genus Nematothallus, Lang (1937) constructed an informal class of plants, the nematophytales, to include these fossils. Strother (1988) further emphasized the differences between the nematophytales and both embryophytes and algae by placing them into a new group, the Paraphyta.

Palynomorph assemblages recovered from the Kanosh Shale at Fossil Mountain, Utah, are dominated by operculate acritarchs and cryptospores with minor smaller acritarchs. The present findings add new data to the largely incomplete knowledge of Ordovician acritarch assemblages from Laurentia, up to now known only from very few localities in North America. These populations contain some species in common with acritarchs from the Canning and Georgina basins in Australia and with assemblages from China; they indicate a Middle Ordovician (Dapingian-Darriwilian) age. The assemblage is lacking many typical marine acritarchs of this age, which, in combination with some cryptospores, is probably reflecting the likelihood of freshwater influence in the Kanosh Basin. This observation is congruent with previous interpretations of the depositional setting of the Kanosh Shale as a shallow water lagoon that supported the deposition of carbonate hardgrounds.

Four new taxa are described: Busphaeridium vermiculatum n. gen., n. sp.; Digitoglomus minutum n. gen., n. sp.; Turpisphaera heteromorpha n. gen., n. sp.; and Vermimarginata barbata n. gen., n. sp. In addition, the abundance of operculate forms has enabled the revision and a new emendation of the genus Dicommopalla and clarification of the “opalla” complex. We also propose new and revised suprageneric taxa that emphasize inferred biological differences among acritarch genera. The Sphaeromorphitae subgroup is emended to include forms lacking sculptural elements. Two new informal subgroups are proposed: the Superornamenti and the Operculate Acritarchs. Cryptospores are abundant throughout the sections studied and they appear to be more closely related to the late Cambrian Agamachates Taylor and Strother than to Darriwilian and younger Ordovician cryptospores from Gondwana.

The early terrestrial fossil record contains numerous Siluro-Devonian problematic Thallophyta which have morphological and habitat characteristics intermediate between the algae and the embryophytic plant kingdom. Three new species of the genus Nematothallus Lang (N. taenia, N. lobata, and N. elliptica) are described from a coaly lens in the Bloomsburg Formation (Ludlow). They are included in the order Nematophytales, which is placed in a new informal taxonomic group, Paraphyta, intended to include enigmatic, terrestrial plant-like fossils. These species designations are based upon the gross morphology of carbonized thalli which consist of an underlying anatomy of flattened tubular elements. The association and attachment of cuticles and axes of ?Prototaxites to Nematothallus is clearly demonstrated in these collections. The morphological and anatomical variety expressed in the numerous fragments of thalli from the deposit implies moderate levels of organic diversity in a “flora” of nonvascular, terrestrial plant-like thallophytes which predates the adaptive radiation of the embryophytes.

Non-marine and marine palynomorphs were collected from a Telychian through Gorstian rock outcrop located near Allenport, Pennsylvania, USA in the east-central part of the Appalachian Foreland Basin. Close sampling of the section revealed six distinct palynological assemblages of spores, cryptospores, acritarchs and prasinophycean algae, likely deposited in nearshore marine settings. The Silurian Period is a critical time in plant evolution as megafossils found elsewhere indicate that vascular plants (tracheophytes) originated during this interval. Palynoflorules generally show a transition from cryptospore-dominated to miospore-dominated assemblages during the latter half of the Silurian. This transition is evident at Allenport, where over 30 species of miospores and cryptospores are recognized, including two new species: Vermiverruspora cottera and Rugosphaera falloambita. The sequential progression of innovations in exine structure and sculpture seen in the nonmarine palynomorphs at Allenport closely matches evolutionary patterns documented previously in the Appalachian Basin, Avalonia, and elsewhere around the world.

The Cryptogamic, or spore-producing, plants of today are composed of three nonvascular, bryophyte groups (mosses, liverworts, and hornworts) and several vascular groups (ferns, club mosses, and horsetails). All of these plants produce abundant spores, which serve as propagules for dispersing and, to some extent, preserving plants through periods of ecological stress. Plant spores are typically formed as the end products of meiosis (reduction division) from a dividing sporocyte, or spore mother cell (smc). Because of this, they typically occur in groups of four, with each individual spore bearing a characteristic trilete, or Y-shaped mark on its common contact surface. Spore walls, composed of an inert, heterogeneous polymer called sporopollenin, are extremely resistant to the chemical vicissitudes of the terrestrial environment. This property of typical plant spores ultimately allows them to be quite abundant in fine grained clastic rocks. Although fossilized spores represent only a small part of the once-living plant, in many cases, they represent an important component of the plant fossil record, especially when the preservation of macroscopic tissues is lacking.