Morphology and Phylogeny of Two Novel Pleurostomatids (Ciliophora,Litostomatea), Establishing a New Genus

Pleurostomatida Schewiakoff, 1896 is a cosmopolitan order of ciliates. In the present study, we investigated two new pleurostomatid species, Apolitonotus lynni gen. et sp. nov. and Protolitonotus clampi sp. nov., with state‐of‐the‐art methods. Apolitonotus lynni lacks its oral extrusomes and its right kineties form an anterior semi‐suture near the dorsal margin. Based on these two features, the new genus Apolitonotus was established within the Protolitonotidae Wu et al., 2017. Protolitonotus clampi differs from its congeners by its size of 80–130 × 15–30 μm, 4–6 left, and 9–11 right kineties, extrusomes arranged along the oral slit, and two macronuclear nodules. Because Litonotus antarcticus possesses an anterior semi‐suture and oral extrusomes, it was transferred to the genus Protolitonotus, becoming P. antarctius comb. nov. (basionym Litonotus antarcticus Song and Wilbert, 2002). Phylogenetic analyses based on SSU rDNA sequences suggest a sister group relationship of P. clampi and the family Kentrophyllidae, and A. lynni is adelphotaxon to Litonotus gracilis, both within the order Pleurostomatida. Based on the new findings, an improved diagnosis for Protolitonotus was also provided.     

Beak from the body chamber of an Early Carboniferous shelled longiconic coleoid cephalopod from Arkansas,USA

Here we report the discovery of an Early Carboniferous (Late Visean) 3D cephalopod beak displaying significant similarity to the lower beak of Recent coleoids. It was uncovered in a fragmentarily preserved, longiconic shell from the Moorefield Formation in Arkansas, USA. This shell comprises a fractured 29‐mm‐long body chamber having a maximum diameter of ~14 mm and showing an indistinct pro‐ostracum‐like structure. The beak‐bearing shell could easily have been mistaken for a bactritid or orthocerid if it were not for a coleoid‐type, weakly mineralized, evidently organic‐rich shell wall which shows a lamello‐columnar ultrastructure of a bulk of shell wall thickness and plate ultrastructure of thin outer layer. The specimen is assigned to an as‐yet unnamed shelled coleoid of a so far unknown high‐level taxonomic group. A partially exposed, 4.0‐mm‐long portion of the beak is the lower beak in oblique view from its left side. It exhibits fractured anthracite‐like black, apparently originally chitin material, helmet‐like general shape, broad hood with narrow shallow median groove and small notch posteriorly, pronounced pointed, non‐biomineralized upside belt rostrum, high shoulder and about a 90–100 degrees jaw angle. A broad hood and massive rostrum emphasize its similarity to the lower mandible of Recent Vampyroteuthis and signify that its unique, among living coleoids, structure has been existed for at least since Late Visean time (~333 my).     

Adaptations for the maintenance of water balance by three species of Antarctic mites

Three species of Antarctic mites, Alaskozetes antarcticus, Hydrogamasellus antarcticus and Rhagidia gerlachei, are abundant in the vicinity of Palmer Station, Antarctica. No single mechanism for reducing water stress was shared by all three species. A. antarcticus and R. gerlachei (both ca. 200 μg) are over twice as large as H. antarcticus (ca. 90 μg), but all had similar body water content (67%) and tolerated a loss of up to 35% of their body water before succumbing to dehydration. All imbibed free water and had the capacity to reduce water loss behaviorally by forming clusters. Alaskozetes antarcticus was distinct in that it relied heavily on water conservation (xerophilic classification) that was largely achieved by its thick cuticular armor, a feature shared by all members of this suborder (Oribatida), and abundant cuticular hydrocarbons. In comparison to the other two species, A. antarcticus was coated with 2–3× the amount of cuticular hydrocarbons, had a 20-fold reduction in net transpiration rate, and had a critical transition temperature (CTT) that indicates a pronounced suppression in activation energy (E _a) at temperatures below 25°C. In contrast, H. antarcticus and R. gerlachei lack a CTT, have lower amounts of cuticular hydrocarbons and have low E _as and high net transpiration rates, classifying them as hydrophilic. Only H. antarcticus was capable of utilizing water vapor to replenish its water stores, but it could do so only at relative humidities close to saturation (95–98 %RH). Thus, H. antarcticus and R. gerlachei require wet habitats and low temperature to counter water loss, and replace lost water behaviorally through predation. Compared to mites from the temperate zone, all three Antarctic species had a lower water content, a feature that commonly enhances cold tolerance.     

Pallenopsis patagonica (Hoek, 1881) – a species complex revealed by morphology and DNA barcoding,with description of a new species of Pallenopsis Wilson, 1881

Pallenopsis patagonica (Hoek, 1881) is one of the most taxonomically problematic and variable pycnogonid species, and is distributed around the southern South American coast, and the Subantarctic and Antarctic areas. We conducted a phylogenetic analysis of mitochondrial cytochrome c oxidase subunit I (COI) sequences of 47 Pallenopsis specimens, including 39 morphologically identified as P. patagonica, five Pallenopsis pilosa (Hoek, 1881), one Pallenopsis macneilli Clark, 1963, one Pallenopsis buphtalmus Pushkin, 1993, and one Pallenopsis latefrontalis Pushkin, 1993. Furthermore, we studied morphological differences between the different COI lineages using light and scanning electron microscopy, including also material from Loman's and Hedgpeth's classical collections, as well as Hoek's type material of P. patagonica from 1881. The molecular results unambiguously reveal that P. patagonica is a complex of several divergent clades, which also includes P. macneilli, P. buphtalmus, and P. latefrontalis. Based on the material available, two major clades could be identified, namely a ‘Falkland’ clade, to which we assign the nominal P. patagonica, and a ‘Chilean’ clade, which is distinct from the ‘Falkland’ clade. We describe the ‘Chilean’ clade as new species, P allenopsis yepayekae sp. nov. Weis, 2013. All molecular results are confirmed by specific morphological characteristics that are discussed in detail and compared with Pallenopsis species closely related to the P. patagonica complex. Our results reveal that P. patagonica is a species‐rich complex that is in need for a thorough taxonomic revision, using both morphological and genetic approaches. © 2014 The Linnean Society of London     

Temperature preferences of the mite, Alaskozetes antarcticus, and the collembolan, Cryptopygus antarcticus from the maritime Antarctic

Abstract. The thermal preferences of Alaskozetes antarcticus (Acari, Cryptostigmata) and Cryptopygus antarcticus (Collembola, Isotomidae) were investigated over 6 h within a temperature gradient (?3 to +13 °C), under 100% relative humidity (RH) conditions. After 10 days of acclimation at ?2 or +11 °C, individual supercooling points (SCP) and thermopreferences were assessed, and compared with animals maintained for 10 days under fluctuating field conditions (?6 to +7 °C). Acclimation at ?2 °C lowered the mean SCP of both A. antarcticus (?24.2 ± 9.1) and C. antarcticus (?14.7 ± 7.7) compared to field samples (?19.0 ± 9.0 and ?10.7 ± 5.2, respectively). Acclimation at +11 °C increased A. antarcticus mean SCP values (?13.0 ± 8.5) relative to field samples, whereas those of C. antarcticus again decreased (?16.7 ± 9.1). Mites acclimated under field conditions or at +11 °C selected temperatures between ?3 and +1 °C. After acclimation at ?2 °C, both species preferred +1 to +5 °C. Cryptopygus antarcticus maintained under field conditions preferred +5 to +9 °C, whereas individuals acclimated at +11 °C selected +9 to +13 °C. For A. antarcticus, thermopreference was not influenced by its cold hardened state. The distribution of field specimens was further assessed within two combined temperature and humidity gradient systems: (i) 0–3 °C/12% RH, 3–6 °C/33% RH, 6–9 °C/75% RH and 9–12 °C/100% RH and (ii) 0–3 °C/100% RH, 3–6 °C/75% RH, 6–9 °C/33% RH and 9–12 °C/12% RH. In gradient (i), C. antarcticus distributed homogeneously, but, in gradient (ii), C. antarcticus preferred 0–3 °C/100% RH. Alaskozetes antarcticus selected temperatures between 0 and +6 °C regardless of RH conditions. Cryptopygus antarcticus appears better able than A. antarcticus to opportunistically utilize developmentally favourable thermal microclimates, when moisture availability is not restricted. The distribution of A. antarcticus appears more influenced by temperature, especially during regular freeze‐thaw transitions, when this species may select low temperature microhabitats to maintain a cold‐hardened state.     

The morphology of gills of Haliotis tuberculata (Linnaeus, 1758)

Manganaro, M., Laurà, R., Guerrera, M.C., Lanteri, G., Zaccone, D. and Marino, F. 2011. The morphology of gills of Haliotis tuberculata (Linnaeus, 1758). —Acta Zoologica (Stockholm) 93 : 436–443. Although the morphology of abalone gills has been studied by some authors, up to date no data are available about the gills of Haliotis tuberculata. This study was carried out, by light and electron microscopy, on 10 wild adult H. tuberculata. Gills lamellae produce an undulated surface increasing the area in contact with water. At the level of skeletal rods, we observed a joint‐like structure that allows a checked movement. The left ctenidium is always decidedly larger than the right, probably because of the enormous size of the shell muscle. The cilia permit oxygenated water that leaves the afferent border and is thrust away at the tips of the lamellae by the extremely long cilia. Ciliary movement may take part in sweeping mucous secretions to capture extraneous particles and remove them from the gills. Three types of mucous cells are distributed along the epithelium of the afferent and efferent zones of the gill filament. They seem to play a role in the cleansing of gills in coordination with the muscle contraction and ciliary movement. The presence of microvilli on particular cells reflects their role associated with the absorption of substances from the environment. A haemolymphatic vessel is located in the central zone of the gill filament. The backbone of the haemolymphatic vessel is a chitino‐like structure, which gives support to the gills.     

Cryptococcus antarcticus var. circumpolaris var. nov., a basidiomycetous yeast from Antarctica

Cryptococcus antarcticus Vishniac & Kurtzman var. circumpolaris Vishniac and Onofri var. nov. (Filobasidiales, Tremellomycetidae, Hymenomycetes), an anamorphic yeast with ca. 73% nDNA relatedness to Cryptococcus antarcticus var.antarcticus, differs in failure to assimilate raffinose, a lower maximum temperature for growth, fatty acid profile, and in a single nucleotide change in the D2 region of LSU rDNA. This revised version was published online in June 2006 with corrections to the Cover Date.     

Sexual,habitat‐constrained and parasite‐induced dimorphism in the shell of a freshwater mussel (Anodonta anatina,Unionidae)

Intraspecific trends in freshwater mussel (unionoid) shells that are consistently associated with differences in the mussels' sex and/or parasitic infestation can potentially be used to reconstruct sex ratios or parasitic levels of modern and ancient unionoid populations. In contrast to morphological patterns within mammal species, such dimorphic trends within unionoid species are, however, poorly understood. This study investigates, for the first time, to what extent sex, trematode infection and indirect habitat effects determine shell morphology in the freshwater mussel Anodonta anatina. Three of the five study populations displayed significant sexual shell width dimorphism. Here, shells of females were significantly wider than males, probably as a result of altered shell growth to accommodate marsupial gills. In two of these populations, female shells were additionally significantly thinner than those of males, which could be a result of resource depletion by offspring production. Two other A. anatina populations showed no significant dimorphic patterns, and our results indicate that this interpopulational difference in the degree of sexual dimorphism may reflect the overarching effect of habitat on morphology. Thus, populations in the most favourable habitats exhibit faster growth rates, attain larger maximum sizes and produce more offspring, which results in more swollen gills and consequently more inflated shells of gravid females compared to less fecund populations. None of the populations showed any evidence for sexual dimorphism in overall size, growth rate, sagittal shape and density of shells. In addition to sexual dimorphisms, infestation by bucephalid trematode parasites (Rhipidocotyle sp.) significantly altered sagittal and lateral shell shape of A. anatina in one of the populations, with infected specimens growing wider and more elongated. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Response of plants and the dominant microarthropod, Cryptopygus antarcticus, to warming and contrasting precipitation regimes in Antarctic tundra

We examined the influence of warming and supplemental precipitation on plant production and abundance of the dominant microarthropod, the springtail Cryptopygus antarcticus (Collembola), in tundra dominated by the vascular plants Colobanthus quitensis and Deschampsia antarctica along the Antarctic Peninsula. Tundra cores were placed in plots near Palmer Station where they were warmed with infrared heaters in combination with receiving supplemental precipitation. Diel canopy air and soil temperatures and air vapor pressure deficits in warmed plots were elevated 0.8 °C, 2.2 °C and 0.13 kPa, respectively. After two growing seasons, total aboveground plant production was greater under warming as a result of enhanced production by C. quitensis, which more than offset declines in moss biomass. Total aboveground plant production was also greater under supplemental precipitation primarily as a result of enhanced moss production. Total aboveground plant production was greatest under the combination of warming and supplemental precipitation, primarily as a result of enhanced C. quitensis production. C. antarcticus were more abundant in cores receiving supplemental precipitation and there was a strong treatment interaction; these springtails were most abundant in warmed cores receiving supplemental precipitation. Over 50% of the variability in the abundance of C. antarcticus could be explained by differences in aboveground plant biomass. However, plant production did not appear directly responsible for differences in C. antarcticus abundance; when we examined C. antarcticus abundance per unit of aboveground plant biomass, differences in its abundance among treatments were still apparent implying these differences were not the direct result of plant biomass. The responses of C. antarcticus were consistent with its known moisture and thermal preferences, suggesting that abiotic factors played a dominant role in controlling its abundance. Precipitation regime had large impacts on warming responses and these were species specific, illustrating the importance of future precipitation regimes in predicting system responses to warming.     

中国仙茅科一新记录种——喜马拉雅仙茅

首次报道中国仙茅科一新记录种——喜马拉雅仙茅(Molineria prainiana Deb),其植株高约170 cm,叶片长60～107 cm,总状花序开展,被长绒毛,长约30 cm,花黄色,子房顶端无喙。该种原记载产自印度和不丹,2019年该种在中国云南西部,铜壁关省级自然保护区发现有分布,凭证标本保存在HITBC。     

Functional differentiation in the anterior gills of the aquatic air-breathing fish, <Emphasis Type="Italic">Trichogaster leeri</Emphasis>

The fish gill is a multifunctional organ responsible for gas exchange and ionic regulation. It is hypothesized that both morphological and functional differentiation can be found in the gills of the aquatic air-breathing fish, Trichogaster leeri. To test this, we used the air-breathing fish, Trichogaster leeri, to investigate various morphological/functional parameters. First, we evaluated the importance of performing the aquatic surface respiration behavior in T. leeri. A reduced survival rate was observed when fish were kept in the restrained cages in hypoxic conditions. On the gross anatomy of gills, we found evidence of both morphological and functional modification in the first and the second gills and are responsible for ionic regulation. There were large-bore arterioarterial shunts in the fourth gill arch. It is specialized for the transport of oxygenated blood and is less responsive to environmental stress. In addition, the anterior and the posterior gills differed in the Na⁺, K⁺-ATPase activity upon ionic stresses. That is, only the Na⁺, K⁺-ATPase activity of the anterior two gills was up-regulated significantly in the deionized water. Lastly, we found that the number of mitochondria-rich cells in the first and the second gills increased following ionic stress and no difference was found in the third and the fourth gills following such an exposure. These results supported the hypothesis that there are morphological and functional differences between anterior and posterior gill arches within the air-breathing Trichogaster leeri. In contrast, no significant difference was found among gills in gross anatomy, filament density and Na⁺, K⁺-ATPase activity in the non-air-breather, Barbodes schwanenfeldi.     

Shrimp (Decapoda,Natantia) occurrence and distribution in the eastern Weddell Sea,Antarctica

Summary 108 successful ground and Agassiz trawl catches were taken between 155 and 2031 m depth in the eastern Weddell Sea on board RV Polarstern in spring and summer (October–February) 1985–1989. In addition, 7 hauls were taken with a semipelagic trawl. Only 19 hauls (16.5%) contained no shrimps. The others yielded large numbers of Notocrangon antarcticus, Chorismus antarcticus, and Nematocarcinus lanceopes as well as 20 Lebbeus antarcticus and 11 specimens of an Eualus species new to science. 8 Pasiphaea scotiae were caught in a pelagic krill trawl. No reptant decapod crustaceans were detected in the study area. Shrimp densities determined from trawl catches were lower than estimates derived from underwater photography but in the same order of magnitude. Although yields of the three common shrimp species in some cases exceeded 20 kg per 0.5 h haul, shrimp stocks in the area cannot be considered to be of commercial significance. A wider geographical distribution and greater frequency of shrimps in high Antarctic waters was found than described hitherto. There was considerable variation in numbers, sex composition, occurrence at different depths, and size-frequency distributions. C. antarcticus and N. antarcticus grow to a larger size compared with individuals from the Antarctic Peninsula area. Within the area of investigation, length frequency distributions are skewed towards larger sizes at higher latitudes. In the eastern Weddell Sea larger specimens of the three common species live at greater depths than smaller individuals. Potential reasons for these differences are discussed.AWI Publication No. 124     

Reproductive biology of caridean decapods from the Weddell Sea

Summary Data on reproductive biology are presented for five benthic caridean shrimps from the high Antarctic (Chorismus antarcticus, Notocrangon antarcticus, Nematocarcinus lanceopes, Lebbeus antarcticus and Eualus kinzeri). The first three species were very common on the Weddell Sea shelf and upper slope, whereas only a few individuals of the other two species were caught-but these did include some ovigerous females. Our measurements include size at first maturity, fecundity (total number and mass of eggs), individual egg mass, egg length, ovary indices, maximum size encountered and documentation of the reproductive cycle in spring and summer. Egg number generally increases with female size, and the largest species (N. lanceopes) also carries the highest number of eggs. The eggs of all high Antarctic species are large, the extreme being L. antarcticus with an egg length of up to 3.3 mm. For C. antarcticus and N. antarcticus, which have wide geographic distributions, a comparison is made with older published and unpublished data from the Subantarctic (South Georgia). High Antarctic representatives of these two species grow to a larger maximum size, attain sexual maturity later in their life cycle, and produce fewer and larger eggs in relation to both carapace length and female mass, than their Subantarctic counterparts.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

Form and function within a phylogenetic framework: locomotory habits of extant predators and some Miocene Sparassodonta (Metatheria)

In this study, we analysed locomotory habits in extant predators and Sparassodonta species through geometric morphometric techniques and discriminant analyses of the distal humerus in anterior view, proximal ulna in lateral view, and tibia in proximal view. We included a wide sample of extant predators, and considered the phylogenetic and allometric structure in the data sets. We also included some Sparassodonta, a group of carnivorous metatherians that inhabited South America during the Cenozoic, and inferred their locomotory habits. Results suggest the presence of a close relationship between shape and locomotory habits, even after removing the shape component explained by phylogeny in the three postcranial elements. Terrestrial habits were inferred for Arctodictis sinclairi, Borhyaena tuberata, ‘Lycopsis’ longirostrus, and Thylacosmilus atrox. Some degree of cursoriality was highlighted in B. tuberata and T. atrox, and climbing abilities in ‘L.’ longirostrus, and to a lesser degree in B. tuberata. Scansorial habits were inferred for Cladosictis patagonica, Sipalocyon gracilis, Prothylacynus patagonicus, and Pseudonotictis pusillus, and in the case of C. patagonica, some digging ability was also tentatively inferred. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 165 , 224–251.     

A new species of Isocyamus (Amphipoda: Cyamidae) from Kogia breviceps (De Blainville, 1838) in Australian waters

Isocyamus kogiae n. sp. is described from a pygmy sperm whale Kogia breviceps (De Blainville, 1838) stranded on Moreton Island, Queensland, Australia. It belongs in the genus Isocyamus because of its white appearance, epaulette-like processes at the anterior dorsum of pereon segment 2, lateral spines on segments 3 and 4, reduced maxilliped, and absence of maxilliped palps, large accessory gills and dentate comb on the dactyle of gnathopod 1. It differs from Isocyamus delphini (Guerin-Meneville, 1836), the only other member of this genus, in that the accessory gills are not equal in length to the main gills, it has no ventral spines, and the dactylus of percopod 1 has a double rather than a single dentate comb. This is the first report of a cyamid from whales of the genus Kogia.     

Histological observations on presumed electroreceptors and mechanoreceptors in the beak skin of the long-beaked echidna,Zaglossus bruijnii.

Sensory receptors in the rostral portion of the beak skin of a single specimen of the rare long-beaked echidna, Zaglossus bruijnii, are described. Mucous glands which have been modified to accommodate sensory innervation, similar to those seen in Ornithorhynchus, are found in the rostral 2 cm of the beak skin, anterior to the maxillofacial foramen, at a density of approximately 12/mm². The papillary epidermal portion of the gland ducts are walled by concentric layers of keratinocytes, and each duct is innervated by 10–15 myelinated nerve terminals. The mucous gland receptors in Zaglossus are intermediate in structure between those of Ornithorhynchus and Tachyglossus, but are similar enough to the former to suggest that electroreception may play a major role in the sensory experience of Zaglossus. Push-rod mechanoreceptors also occur throughout the same region of beak skin, and appear similar to those described for Tachyglossus.     

Morphology and diet are decoupled in nearshore notothenoids from King George Island,West Antarctica

Antarctic notothenioid fishes show wide adaptive morphological radiation, linked to habitat preferences and food composition. However, direct comparisons of phenotypic variability and feeding habits are still lacking, particularly in stages inhabiting nearshore areas. To assess these relationships, we collected juveniles and adults of the most common benthic species inhabiting shallow waters off the South Shetland Islands within a similar size range, the plunderfish Harpagifer antarcticus, the black rockcod Notothenia coriiceps, and the marbled rockcod Notothenia rossii. Individual size ranges varied from 44.0 to 98.9 mm standard length (LS) (H. antarcticus), from 95.8 to 109.3 mm LS (N. coriiceps), and from 63.0 to 113.0 mm LS (N. rossii). Notothenioid fish showed different morphospace variability, being larger for H. antarcticus than the other Notothenia species and associated with the position of the posterior end of the operculum, along with the location and relative size of the eye. The evolutionary allometry was low, but the static allometry was much higher, especially for H. antarcticus and N. rossii. The diet was mainly carnivorous, consisting of amphipods and euphausiids. Macroalgae were scarce or totally absent in the gut contents of all species. Only H. antarcticus showed an increase in the prey number and ingested prey volume with fish size. Finally, there was a significant covariation between shape changes and LS in all species (allometric effects), however, not with prey composition, probably due to the small size range or ontogenetic stage and the relative similarity (or lack of contrast) in the benthic environment that they utilized.     

Morphological development of glochidia in artificial media through early juvenile of freshwater pearl mussel,Hyriopsis (Hyriopsis) bialatus Simpson, 1900

The morphological development and the sequence of organogenesis from glochidium to the early juvenile stage of the freshwater pearl mussel, Hyriopsis bialatus, were observed. Larvae of H. bialatus were cultured in standard tissue culture medium (M199) supplemented with common carp (Cyprinus carpio) plasma and they showed transformation within 10 days. Larval samples were collected every 2 days during glochidia development and subjected to histological processing. Three types of cell masses were developed during this period: the ventral plate (the foot rudiment), lateral pits (the gill rudiment), and the oral plate or endodermic sac (the origin of the digestive tract). The ventral plate gave rise to two foot lobes which fused into a single lobe. The gills were developed from the lateral pits next to the ventral plate, forming a pair of gill buds that became elongated and turned into gill bars. The digestive tract began with the formation of mouth by invagination of the oral plate (or endodermic sac) and formation of a tube underneath the growing foot. Several controversial aspects of organogenesis have been inferred, e.g., de novo formation of the anterior and posterior juvenile adductors, the fate of the mushroom body structure, and foot lobe formation from two separate precursor lobes. A mushroom body protruded into the mantle cavity and remained there throughout the transformation period. Moreover, the evidence of a supporting band (mucoid structure) in the mature glochidium of H. bialatus has never been reported in other freshwater mussel species, and its function and composition need to be further investigated.     

Structure and formation of the adventitious tube of the Japanese watering-pot shell Stirpulina ramosa (Bivalvia, Anomalodesmata, Clavagellidae) and a comparison with that of the Penicillidae

Abstract. Stirpulina ramosa is the only extant endobenthic representative of the Clavagellidae and is restricted to the waters of Japan. A single intact adventitious tube of this species has been obtained and its structure is described. The right valve is 16 mm long and located within the adventitious tube. It has an opisthodetic ligament located on resilifers. There are anterior and posterior adductor muscle scars, a thick pallial line, and pallial and pedal gape (right valve only) sinuses. The left shell valve is but 9 mm long and is united into the fabric of the adventitious tube via the intermediary of a shelly saddle. Internally, only the anterior adductor muscle scar and a small element of the pallial line scar are identifiable on the left valve. The posterior adductor and the rest of the pallial line scar (including a pallial sinus) are, remarkably, located on the adventitious tube beyond the shell valve margin. The adventitious tube of S. ramosa is formed in a manner wholly dissimilar from that of Brechites vaginiferus (Penicillidae). In B. vaginiferus, the tube is secreted as a single entity from the general outer mantle surface, including the siphons, covering the body. As a consequence, both shell valves are incorporated into the structure of the tube and the watering pot is bilaterally symmetrical. In S. ramosa, the tube and watering pot are secreted from the mantle margin and surface surrounding and extending from the left shell valve, so that only the left valve is incorporated into its structure. A dorsally derived mantle element is progressively extended over to the right side of the body, meeting a ventrally derived counterpart that passes beneath it, forming a pleat in the calcareous structure of the right side of the tube that they secrete. This pleat extends into the complex of watering‐pot tubules and forms the pedal gape. The watering pot is thus Ω shaped. The ventrally derived mantle element forms a sinusoidal crest on the right‐hand base of the watering pot, creating a pedal gape sinus scar on the right valve. The Clavagellidae radiated widely in the Mesozoic, leaving behind a rich fossil record for Stirpulina. Only S. ramosa, however, has survived until the present. In contrast, the Cenozoic Penicillidae has a poor fossil record, but there is a rich variety of extant endobenthic watering‐pot shells. It has been argued hitherto that the two families represent a remarkable example of convergent evolution. In view of the success of the Penicillidae and thus the endobenthic, tube‐dwelling lifestyle, however, it is hard to understand why Stirpulina has largely died out—even S. ramosa being known by but one or two specimens. A study of the anatomy of S. ramosa might one day answer this question.