Search

ANASPIDES RICHARDSONI The following descriptions explicitly refer to a detailed examination of the right Thp1 of two adult female individuals of A. richardsoni. Comparative surveys of the posterior thoracopods have been made in several specimens of A. richardsoni, Anaspides tasmaniae (Thomson, 1893) and Anaspides clarkei Ahyong, 2015 (see Grams & Richter, 2021). Cuticle and skeletal structures of thoracopods in Anaspides The first pair of thoracopods (Thp1) in A. richardsoni (Fig. 2A) shows some gnathal modifications, while the following (‘posterior’) thoracopods conform to typical ‘pereiopods’. The following description refers to both types of legs, if not specified otherwise (for a detailed depiction of posterior thoracopods, see Grams & Richter, 2021). The thorax connects and articulates with the coxa as an almost square cuticular ring. Anterolaterally, the cuticle of the thorax appears of somewhat lesser robustness (Fig. 2B). The thorax in the posterior thoracomeres (Thp2–8, respectively) continues into a lateral plate with similar properties, whereas in the first thoracomere the thorax continues into the posterior end of a notably cuticulized carapace-like fold (a short lateral and ventrally oriented overlap of the thoracic cuticle) that reaches anteriorly up to the rostrum. Medially, the thoracic cuticle of the left and right body half is coalesced to a sternum (Fig. 2B) that forms a shared roof-like apodeme posteromedially by being curved dorsally and anteriorly (see partly dashed curved arrow and dashed outline, Fig. 2B). The thoracopodal protopod comprises a coxa, an intrabasis and a basis. The coxa is mainly embodied by two notably robust components: an anterior plate (aCo in Figs 2A–C, 3B) and a posterior plate with a distinct invagination (pCo in Figs 2B, D, 3A, C). The cuticle of the coxa is apparently less robust and more membranous in the medial to posteromedial and posterolateral to lateral areas (Fig. 2B), but in Thp1 the medial to posteromedial area is largely covered by the robust plates and sclerites of the endites (see next paragraph). In the posterior thoracopods, the anterior coxa plate connects and articulates laterally and anteromedially with the thorax, whereas in Thp1 it is indirectly connected medially to the thorax via a sclerite of the proximal endite. The lateral articulation present in the posterior thoracopods is missing in Thp1, and the transition between the thorax and the anterior coxa appears smooth and ambiguous, without a clear interpodomere membrane. The posterior invagination of the coxa in the posterior thoracopods extends proximally into an anteriorly directed noselike apodeme. No such apodeme is present in Thp1 (Fig. 2B). Instead, the invagination forms a posterior condyle at the proximal coxa margin that articulates with the thorax (Fig. 2B, D). The joint constellation between thorax and coxa in the posterior thoracopods results in a lateromedial articulation axis allowing promotion and remotion. In Thp1, this axis (ax Th-Co in Fig. 2B–D) is (in comparison) rotated by almost 45°, resulting in a combined motion of promotion with abduction and remotion with adduction, respectively. On its distal margin, the coxa forms a bicondylar articulation with the intrabasis (Fig. 2B), with an anterior condyle at the anterior coxa plate (the condyle being more strongly invaginated in Thp1; Fig. 2A–C) and a posterior condyle at the posterior coxa invagination (Fig. 2B, D). In females, an endite attaches medially on the coxa of thoracopods 5–7. It is lobate, moderately cuticulized and carries long, distally and slightly anteriorly directed setae. These endites are missing or at least much less prominent on the other ‘pereiopods’ and in males in general. However, on Thp1 two endites are present (in both sexes), together with a somewhat complex construction of plates and sclerites: the proximal endite appears leaf-like (pEn in Fig. 3B, C), whereas the distal endite is more or less tetrahedral (dEn in Fig. 3B, C). Both these endites have a distinct proximal plate (or stem), from which they arise (St* and St** in Fig. 3C). The plate of the proximal endite connects and articulates posterolaterally with the posterior coxa plate (Fig. 2D; left white arrow in Fig. 3C), medially with the distal endite (right white arrow in Fig. 3C) and anteromedially, via a sclerite, with both the anterior coxa plate and the thoracic sternum (Fig. 2C, D, 3B). The plate of the distal endite reaches posterolaterally into the membranous area of the coxa (without connecting to the posterior coxa plate; Fig. 2D; St** in Fig. 3C), in addition to forming anterolaterally a shared condyle with both the anterior coxa plate and the intrabasis (Fig. 2D; white arrow in Fig. 3B). The distal edge of the proximal endite and the distal triangular surface of the distal endite are both setose. Laterally attached to the coxa are two leaf-like epipods, with the second epipod originating distally to the first, while being positioned anteriorly to it (pEp and dEp in Fig. 3). In the posterior thoracopods, the epipods originate close to each other, whereas they are positioned far more apart proximodistally in Thp1 (pEp and dEp in Fig. 2A–D). Each epipod has a stem, which is clearly distinct from the distal portion. Although the epipods are only weakly cuticulized overall, the stem appears to be more strongly cuticulized than the rest. Anteriorly, the stem of the distal/anterior epipod is articulated with the coxa via a rhombus-shaped sclerite, which appears to be absent in Thp1. The intrabasis is a robust half-ring covering the anterior, lateral and posterior wall of the leg (InB in Fig. 2B), leaving the medial side between the coxa and basis mostly membranous. A bicondylar articulation between the intrabasis and the basis (ax InB-Ba in Fig. 2B–D) is formed by an inwardly folded anterolateral edge and a posteromedial articulation point. The basis (Ba in Fig. 2A–D) takes up about twothirds (almost three-quarters in Thp1) of the total length of the protopod. A bicondylar articulation with the endopod (i.e. the ischium) is formed by robust anterolateral and posteromedial articulation points. However, in Thp1, the posteromedial articulation point is apparently absent (Fig. 4A, B). Here, strongly cuticulized edges are present, but without being in (at least not permanent) contact, possibly resulting in some type of ‘sliding-edge’ articulation. The proximal margin of the basis comprises a robust half-ring covering the anterolateral, anterior, medial and posteromedial edges. The rest of the basis also appears to be strongly cuticulized, although less robust compared wth the proximal margin. Both the intrabasis and basis of Thp1 generally appear to be of higher robustness than in the posterior thoracopods, with the anterior wall of the basis being prominently concave, more or less fitting the form of the distal coxal endite and the anteriorly adjacent maxilla, while the narrow medial wall is densely setose. Within the lateral membrane between the basis and the intrabasis of Thp1–7, an exopod attaches laterally. The exopod of Thp 2–6 comprises a prominent peduncle and a long, feathered flagellum, whereas in Thp1 and Thp7 it comprises only a short stem, followed by a longish lamellar portion (Ex in Fig. 3A). In Thp2–6, the exopod articulates with the basis via an anterior hinge and a posterior rhombusshaped sclerite. Both these articulation structures are missing in Thp1. The endopod consists of the ischium, merus, carpus, propodus and dactylus and, for the most part, accords between Thp1 (Fig. 4A–D) and the posterior thoracopods. The ischium (Is in Figs 2A, 4A) measures less than half the length of the basis. A bicondylar articulation with the merus is formed by an anteromedial and a posterolateral articulation point (ax Is-Me in Fig. 4A). The merus (Me in Figs 2A, 4A) somewhat exceeds the length of the basis. A bicondylar knee-like articulation with the carpus is formed by anteromedial and posterolateral articulation points, respectively (ax Me-Ca in Fig. 4A). The carpus (Ca in Figs 2A, 4A) measures about half the length of the basis. Posteriorly on its proximal margin, a broad sclerite reaches distally into the propodus, serving as an attachment site for muscle MC2. The carpus articulates distally with the propodus via an anterior condyle (white arrow in Fig. 4A, C, D) and a complex posterior construction: a posterolateral sclerite (cBr in Fig. 4A, C, D) connects the distal margin of the carpus to a cuticular half-ring (cHr in Fig. 4A, C, D) that is positioned posteriorly at and articulating medially and laterally with the proximal margin of the propodus (m* and l* in Fig. 4A, C, D). Two sclerites (not depicted) arise slightly proximal to the medial and lateral joints, functioning as attachment sites for muscles CP2 and CP4. The propodus (Pr in Fig. 4A, C, D) measures about three-quarters of the length of the basis. A bicondylar articulation with the dactylus is formed by slightly posteromedial and posterolateral articulation points (ax Pr-Da in Fig. 4A). The dactylus (Da in Fig. 4A, C) is short and of robust cuticle, ending in a lateromedial row of four (six in Thp1) strong, cuspidate setae of alternating length (Figs 1A, 3A), giving it a clawed or almost hand-like appearance. Posteriorly, on its proximal margin, a longish sclerite (not depicted) reaches into the distal third of the propodus, functioning as attachment sites for muscles CD1 and PD1. Musculature of Thp 1 in Anaspides In the right Thp1, a total of 33 extrinsic and intrinsic muscles were identified (Figs 5, 6; for a detailed description, see Table 2). A total of 13 extrinsic muscles connect the thorax with the leg (i.e. with the protopod; Fig. 5A, B). Six of these muscles (TC1–6) insert on the coxa, with two of them more specifically on the posterior invagination (TC1 and TC5) and one (TC6) on a ligament that connects the posterior invagination of the coxa with the slight depression of the anterior coxa wall. A further two of the 13 extrinsic muscles insert on the proximal coxal endite (TC2) and the distal epipod (TEp1), respectively. The remaining four muscles insert on the intrabasis (TIn1) and the basis (TB1–3), respectively. Of the 20 intrinsic leg muscles, ten originate in the protopod (Figs 5A, B, 6A). Seven of these originate from the coxa (CIn1, CIn2 and CB 1– CB 5), with two (CIn1 and CIn2) inserting on the intrabasis and five (CB 1– CB 5) on the basis. One of these intrinsic muscles (CIn1) connects the proximal coxal endite with the intrabasis. Only one muscle (InB1) directly connects the intrabasis with the basis. Another two muscles originate in the basis and insert on the proximal margin of the ischium (BIs1 and BIs2). No muscles are extrinsically or intrinsically associated with the exopod. Intrinsic to the endopod, 11 muscles are present (Fig. 6A–C). Two of these muscles connect the ischium with the merus (IsM1 and IsM2; Fig. 6A, B) and two connect the merus with the carpus (MC 1 and MC 2; Fig. 6B, C). Five muscles originate in the carpus, with four of them inserting on the proximal margin of the propodus (CP1–4) and one muscle (CD1) reaching onto the proximal margin of the dactylus (Fig. 6B, C). A further two muscles connect the propodus with the dactylus (PD 1 and PD 2; Fig. 6C)., Published as part of Grams, Markus, Klinger, Michael & Richter, Stefan, 2023, Neither leg nor jaw-nor always the same: a critical revision of the eumalacostracan maxilliped, pp. 965-1004 in Zoological Journal of the Linnean Society 197 (4) on pages 969-974, DOI: 10.1093/zoolinnean/zlac083, http://zenodo.org/record/7797605, {"references":["Thomson GM. 1893. On the freshwater schizopod from Tasmania. Transactions of the Linnean Society. 2 nd Series: Zoology 6: 285 - 303.","Grams M, Richter S. 2021. Locomotion in Anaspides (Anaspidacea, Malacostraca) - insights from a morphofunctional study of thoracopods with some observations on swimming and walking. Zoology 144: 125883."]}

STYGIOMYSIDA: SPELAEOMYSIS BOTTAZZII The first pair of thoracopods (Thp1) is modified in comparison to the third to eighth pairs (Thp3–8) of pediform thoracopods, while Thp2 has a somewhat intermediate morphology. The following description is based on a detailed examination of the right first thoracopod of one female of S. bottazzii (Fig. 15). Cuticle and skeletal structures of Thp 1 in S. bottazzii The more or less rectangular protopod (almost as wide as long) of S. bottazzii consists of the coxa (one-third) and basis (two-thirds of the total length of the protopod). It appears clearly separated from the thorax, although our examination allowed no specific statement on the articulation or connection of the thorax and coxa. The coxa (Coin Fig. 15C) appears as a broad ring with a slightly protruding distomedial margin. Laterally, a lamellar, elongate epipod attaches (Ep in Fig. 15C). It broadens somewhat in the anterodorsal direction shortly after its narrow stem, continues as a longish blade with a concave posterodorsal surface and narrows distally into an anterodorsal tip. Its proximal and anteroventral margins appear strongly cuticulized. The basis (Ba in Fig. 15C), from a posterior perspective, appears about as long as wide. Its anteromedial distal margin, however, extends into a prominent distally directed setose endite almost as long as the ischium and merus together, covering part of the anterior surface of the ischium. A lamellar leaf- or spade-shaped exopod attaches proximolateral on the basis (Ex in Fig. 15C). It is almost as long as the basis, with flat anterior and posterior surfaces. It carries two distally directed setae on its tip and a row of finer setae on its dorsal margin. The crescent-shaped endopod consists of the ischium, merus, carpus, propodus and dactylus. In relationship to the following podomeres, the ischium appears short (Is in Fig. 15C). Anteromedially, however, its distal margin extends into a prominent distally directed setose endite almost as long as the merus, covering part of the anterior surface of the merus. With the medial side of the ischium being about twice as long as its lateral side, its distal margin is displaced by ~35° in the lateral direction. The merus (Me in Fig. 15C) measures about two to three times the length of the ischium. Distomedially, it protrudes into a setose lobe, but is not as prominent as the endites of the basis and ischium. The distal opening of the merus is not oriented distally but displaced ~90° in the lateral direction. The carpus (Ca in Fig. 15C) is slightly longer than the merus. Its proximal margin (connected to the merus) faces medially, whereas its distal margin faces in the distal direction. The propodus (Pr in Fig. 15C) is about as long as the merus and has a somewhat bulged and setose medial margin. The distal margin of the propodus is oriented in the medial direction. The dactylus (Da in Fig. 15C) is slightly shorter than the propodus. It curves somewhat medially and tapers into a distal tip. Four cuspidate setae are present anterodistally. No articulations could be recognized in the present analysis. Judging from the musculature (Fig. 15A), all the endopodal joints seem to be movable in an anterior–posterior axis (i.e. performing adduction/ abduction)., Published as part of Grams, Markus, Klinger, Michael & Richter, Stefan, 2023, Neither leg nor jaw-nor always the same: a critical revision of the eumalacostracan maxilliped, pp. 965-1004 in Zoological Journal of the Linnean Society 197 (4) on pages 993-995, DOI: 10.1093/zoolinnean/zlac083, http://zenodo.org/record/7797605

Grams, Markus, Klinger, Michael, Richter, Stefan (2023): Neither leg nor jaw-nor always the same: a critical revision of the eumalacostracan maxilliped. Zoological Journal of the Linnean Society 197 (4): 965-1004, DOI: 10.1093/zoolinnean/zlac083, URL: https://academic.oup.com/zoolinnean/article/197/4/965/6795015

LOPHOGASTER TYPICUS The first pair of thoracopods (Thp1) is highly modified compared with the posterior pairs (Thp2–8) of pediform thoracopods. Owing to this strong morphological difference, the following descriptions relate only to Thp1, based on a detailed examination of the right Thp1 of three adult males of L. typicus. Cuticle and skeletal structures of Thp 1 in L. typicus The more or less rectangular protopod (more than twice as wide as long) of L. typicus consists of the coxa (twothirds) and basis (one-third of the total length of the protopod). The thorax connects and articulates with the coxa by a cuticular half-ring, leaving the lateral area membranous (Th in Fig. 10A, B). Posteriorly, the cuticle of the thorax is invaginated as a lateromedial fold, forming a short roof-like apodeme (black arrows in Fig. 10A; partly dashed curved arrows and dashed line in Fig. 10B). The coxa does not form a complete ring but has the medial to anteromedial area membranous (Co in Fig. 10A). A bicondylar articulation with the thorax is formed by an anterolateral and posteromedial articulation point, respectively (*l, *m and ax Th-Co in Fig. 10A). Posteriorly, the coxa forms an invagination, which appears as a linear lateromedial furrow (white arrows in Fig. 10A) that ends posterolaterally in a roundish depression. Distally, the podomere articulates anterolaterally and posteromedially with the basis (*l, *m and ax Co-Ba in Fig. 10B). Laterally, a huge lamellar epipod (Ep in Fig. 10A) is attached to the coxa. It is broadly flattened anteroposteriorly and long, reaching at least double the length of the exopod (see below, this section). The epipod articulates with the coxa via two sclerites: anteriorly, a rod-shaped sclerite (S 1 in Fig. 11A, B) forms a dorsal articulation point, while a second ventral sclerite (S 2 in Fig. 11A, B) interlocks the epipod anteriorly on the coxa. The area between both sclerites is membranous. More distally on the epipod, several sclerites form the ‘frame’ of its lamellar distal portion (Ep in Figs 10A, 11B). The basis, from a dorsal perspective, appears roughly drop-shaped, with the medial side being the spherical part, narrowing towards the lateral side (Ba in Fig. 10C). Here, the proximal margin of the basis widens again into a V-shape, ending in two fingers, of which the posterior one serves as attachment site for three muscles (TB1, CB2 and CB3; Fig. 11C). The lateral wall appears membranous (Fig. 10B, C). The distal opening of the basis into the endopod is found in the medial third of the podomere (Fig. 10C). Here, a bicondylar articulation with the endopod (i.e. the ischium) is formed by an anteromedial and a posterior articulation point, respectively (ax Ba-Is in Fig. 10C). A lamellar exopod attaches at the lateral membrane of the basis via a short proximal stem (Ex in Fig. 10A) that articulates with the anteromedial finger-like extension of the basis via a hook-like structure (Fig. 10C). The stem is followed by a much longer distal portion (almost as long as the endopod), which is shaped as an anteroposteriorly flattened blade with a setose distal tip. Table 3. Continued Muscles are characterized by their proximal and distal attachment sites. Relative size (compared with one another, based on circumference) is specified by one (/ = ‘small’) to three (/// = ‘large’) slashes. The crescent-shaped endopod consists of the ischium, merus, carpus, propodus and dactylus. In relationship to the following podomeres, the ischium appears short (Is in Fig. 10A). An articulation with the merus is created by an anteromedial articulation point. Although the podomeres are in close contact posterolaterally, no clear articulation point can be made out. Nonetheless, this closeness might be sufficient to achieve the functionality of a bicondylar joint. The merus (Me in Fig. 10A) measures about twice the length of the ischium. Its distal opening is not oriented distally but is displaced ~90° in the lateral direction. Anteromedially, the podomere is covered with strong, cuspidate setae. A bicondylar articulation with the carpus is formed by an anteromedial and posterolateral articulation point, respectively. The carpus (Ca in Fig. 10A) is about twice the length of the merus. Four long cuspidate setae are attached medially. Its proximal margin (connected to the merus) faces medially, whereas its distal margin faces in the distal direction, articulating with the propodus by an anterior and posterolateral articulation point, respectively. The propodus (Pr, dotted outline in Fig. 10A) is shorter than the carpus and roughly as long as the merus. Three long, cuspidate setae are attached medially. The distal margin of the propodus is slightly oriented in the medial direction, where the podomere is connected with the dactylus by an anterolateral and a posterior articulation point, respectively. The dactylus (Da in Fig. 10A) is almost equal in length to the propodus. The podomere tapers towards its distal tip, where a strong and cuspidate seta is present, while four smaller cuspidate setae cover the dactylus medially., Published as part of Grams, Markus, Klinger, Michael & Richter, Stefan, 2023, Neither leg nor jaw-nor always the same: a critical revision of the eumalacostracan maxilliped, pp. 965-1004 in Zoological Journal of the Linnean Society 197 (4) on pages 981-984, DOI: 10.1093/zoolinnean/zlac083, http://zenodo.org/record/7797605

MEGANYCTIPHANES NORVEGICA The first pair of thoracopods (Fig. 7A) to Thp7 are all similar, whereas Thp8 is vestigial. The following descriptions are based on a detailed examination of the right Thp1 of three adult females of M. norƲegica. Cuticle and skeletal structures of thoracopods in M. norvegica The following description refers collectively to Thp1–7, if not specified otherwise. The ventral cuticle of the first thoracomere is coalesced with that of the cephalon. The density of the cuticle of this cephalothoracic sternum appears higher than in the posterior thoracomeres. Anteriorly, the thoracic cuticle articulates with the maxilla, which is tightly fitted against the anterior wall of the coxa and basis of Thp1. In all thoracomeres, the posterior thoracic cuticle is folded in an anterior direction, forming a broad roof-like apodeme (partly dashed curved arrow in Fig. 7B, C) of moderate density that hangs over the posterior half of the proximal foramen of the leg (i.e. of the coxa). Medially, the cuticle of the thorax forms a posterolaterally and dorsally directed finger-like extension (dashed black outline on Th in Fig. 7B). The protopod of M. norƲegica comprises a coxa (onethird) and a subdivided basis (two-thirds of the total length of the protopod). The coxa is predominantly made up of its more solid distal margin, which forms a half-ring reaching from posterior over medial to anterolateral (Co in Fig. 7D), where it connects to a plate of less dense cuticle. From the anterolateral corner of this plate, a solid cuticular beam reaches dorsad (Cb in Fig. 7C, D) and articulates with the thorax (*l in Fig. 7B–D). Posterolateral on the coxa, an epipod arises, which on Thp1 is plate-like (Ep in Fig. 7A, B), extending somewhat dorsad, but mostly ventrad (almost reaching the exopod). On the posterior thoracopods, the epipod splits into two coiled branches (one dorsal and one ventral) that ramify into several smaller filaments; on Thp6–8, the epipods show the highest complexity, with an additional ventral off-branch that ramifies in a similar way. Medially attached to the coxa of Thp1, a setose endite is present (En, Fig. 7A, C). The endite forms the medial articulation point with the thorax, immediately beneath the finger-like extension (*m in Fig. 7B). On the following thoracopods, the endite is much smaller, if present at all (Fig. 7E). Apart from the cuticular half-ring constituting the distal margin of the coxa, its anterior and posterior parts are mostly membranous, with two (posterior and posterolateral) invaginations. The posterolateral invagination forms a tight proximodistal fold, which expands into the central space of the coxa (curved arrows in Fig. 7D), where it forms a solid and highly complex endoskeletal structure (dark blue part of Co in Fig. 7B–D; see also the Supporting Information, Video S1). Starting from a posterolateral arm, the structure reaches into the centre of the coxa, where it expands into the dorsal and ventral directions. Dorsally, it reaches onto the roof-like apodeme of the thorax. Ventrally, it reaches onto the proximal margin of the basis by extending another two straight arms in anterior and posterior directions. Table 2. Continued Muscles are characterized by their proximal and distal attachment sites. Relative size (compared with one another, based on circumference) is specified by one (/ = ‘small’) to three (/// = ‘large’) slashes. The basis comprises a solid distal part (Ba in Fig. 7A–E), whereas its proximal part (InB in Fig. 7C–E) consists of three posterior and lateral plates and a broad anterior part. Owing to the resemblance to the anaspidan intrabasis, the proximal part(s) of the basis are referred to as the intrabasis in the following description. The anterior part of the intrabasis is separated from the larger distal basis by an inconspicuous furrow (dashed white line in Fig. 7C, E). Anteriorly, it forms a small bulb at its proximal margin (Fig. 7E), into which the anterior arm of the coxal endoskeleton reaches. Proximal to the anterior bulb, at the proximal margin of the intrabasis, sits a somewhat triangular plate (white outline on InB and partly dashed curved arrow in Fig. 7C), which articulates with the coxa (a + in Fig. 7C). Another articulation point is realized between the coxa and the posteromedial plate of the intrabasis (p + in Fig. 7D), resulting overall in a bicondylar coxa–intrabasis articulation (ax Co-InB in Fig. 7B). The medial cuticle of the distal basis appears robust, whereas laterally it is mostly membranous. In this area, two rigid, finger-like structures emerge (one posterolateral and another distoanterolateral) and articulate with two hook-like structures of the exopod (Fig. 7B, C; see also Supporting Information, Video S1). The posterolateral articulation is supported by a longish sclerite positioned immediately distal to the posterolateral finger. The medial cuticle of the distal basis appears robust and carries numerous setae. Distally, the basis is coalesced with the endopod (i.e. with the ischium), with a clear suture but no interpodomere membrane or articulation points (Fig. 7C, D). Within the lateral membrane of the distal basis, the exopod attaches (Ex in Fig. 7A–D). Its peduncle comprises a short posteroventral stem and a much longer distal portion, followed by the flagellum. The peduncle is anteroposteriorly flattened and has a prominent distodorsal pointed protrusion. Proximally, the peduncle articulates with the basis both anterolaterally and posterolaterally via hook-like structures (one from the peduncle stem and one from the distal portion) that are interlocked with the finger-like structures of the distal basis (short arrow in Fig. 7B; see also Supporting Information, Video S1). The endopod consists of the ischium, merus, carpus, propodus and dactylus. The ischium (Is in Figs 7A, 8A) is about twice as long as the protopod. Anteriorly, the ischium forms an articulation with the merus (arrow in Fig. 8D). However, posteriorly an articulation point is not clearly identifiable. Nevertheless, the proximal margin of the merus forms a prominent posterolateral protrusion, which overlaps slightly with the distal margin of the ischium (dashed line in Fig. 8D). The merus (Me in Fig. 8A) appears slightly longer than the ischium. Two long sclerites/tendons emerge laterally and medially from the proximal margin of the merus and reach far into the ischium. A bicondylar articulation with the carpus is formed by a medial and a lateral articulation point, respectively (ax Me-Ca in Fig. 8A). The carpus (Ca in Fig. 8A) measures approximately one-third of the total length of the merus. One short and two long sclerites/tendons emerge anteriorly (long) and posteriorly (long and short) from the proximal margin of the carpus and reach far into the merus. The distal margin forms anteriorly a noselike condyle that articulates with a broad anterior depression at the proximal margin of the propodus (Fig. 8B, C). A thin, longish sclerite articulates laterally with the distal margin of the carpus and posteriorly with the proximal margin of the propodus (Fig. 8B, C). Combined, these structures probably realize a somewhat less restricted bicondylar articulation. the furrow between the intrabasis and basis; black lines emphasize individual plates of the coxa; white lines and partly dashed curved arrows emphasize the posterior thorax apodeme and the proximal anterior triangular plate of the intrabasis. D, posterior view; dashed white line emphasizes the posterior plates of the intrabasis; dashed white circle indicates the anterior bulb of the intrabasis; black lines emphasize individual parts of the coxa and the margins of the intrabasis; curved arrows indicate posterolateral coxa invagination. E, Thp3, anterior view; dashed line emphasizes the furrow between intrabasis and basis. Abbreviations: a*, anterior articulation point; ant, anterior; ax, articulation axis between […]; Ba, basis; Ca, carpus; Cb, proximolateral cuticular beam of coxa; Co, coxa; Da, dactylus; dis, distal; En, endite; Ep, epipod; Ex, exopod; InB, intrabasis; Is, ischium; l* and *l, lateral articulation point; lat, lateral; *m, medial articulation point; Me, merus; med, medial; p*, posterior articulation point; Pr, propodus; prox, proximal; Th, thorax. The propodus (Pr in Fig. 8A) is about twice as long as the carpus. One short and three long sclerites/ tendons emerge from the anteromedial, posteromedial, anterolateral (all three long) and posterolateral (short) corners of the proximal margin of the propodus and reach into the carpus. The propodus articulates with the dactylus by a medial and a lateral articulation point, respectively (ax Pr-Da in Fig. 8A). The dactylus is about half the length of the propodus in Thp1 (Da in Figs 8A, 9E) and somewhat longer than half the propodus in the posterior thoracopods. Two long sclerites/tendons emerge anteriorly and posteriorly from the proximal margin of the dactylus and reach into the propodus. The podomere tapers from its proximal to its distal margin, except for Thp2, where it is more lateromedially flattened, forming a slight distoposterior bulge before tapering towards a distoanterior tip., Published as part of Grams, Markus, Klinger, Michael & Richter, Stefan, 2023, Neither leg nor jaw-nor always the same: a critical revision of the eumalacostracan maxilliped, pp. 965-1004 in Zoological Journal of the Linnean Society 197 (4) on pages 974-981, DOI: 10.1093/zoolinnean/zlac083, http://zenodo.org/record/7797605

PRAUNUS FLEXUOSUS The first and second thoracopods (Thp1 and Thp2) are modified in comparison to the third to eighth pairs (Thp3– 8) of pediform thoracopods. The following descriptions relate only to Thp1, based on a detailed examination of the right Thp1 of five male individuals of P. flexuosus. Cuticle and skeletal structures of Thp 1 in P. flexuosus The more or less rectangular protopod (more than twice as wide as long) consists of coxa and basis. The thorax cuticle proximal to the coxa is robust medially, anteriorly and posteriorly, but membranous laterally. The coxa is formed as a narrow, incomplete proximal ring of moderate robustness, open (i.e. membranous) anteromedially. The ends of the open ring are in contact with the thorax posteromedially and anteriorly, potentially establishing two articulation points, which would form a bicondylar articulation, mostly for adduction/abduction. Anteriorly, the narrow coxa is almost entirely hidden by the thorax. Posteriorly, the coxa forms a transversal invagination from its most medial to its most lateral extent (pCo in Fig. 13B, C), where it forms an articulation with the epipod. Proximally to that articulation, the coxa continues by curving around the lateral side into the membranous area of the thorax and towards anterior. From its most lateral point, a sclerite reaches dorsad and forms another articulation with the epipod. Distal to the posterior invagination of the coxa, a wide membrane (mem in Fig. 13B) connects the coxa to the basis. Posteromedially within this membrane sits a sclerite (presumably a fragment of the coxa), apparently articulating the basis with the thorax (Sc in Fig. 13C). Muscles are characterized by their proximal and distal attachment sites. Relative size (compared with one another, based on circumference) is specified by one (/ = ‘small’) to three (/// = ‘large’) slashes. Laterally attached to the coxa, a lamellar epipod is present (Ep in Fig. 13A, B). Dorsally, it forms an articulation via a sclerite with the lateral coxa, while posteriorly, it articulates with the lateral extent of the coxa invagination. An anterior contact point with the lateral basis (lBa in Fig. 13A) might constitute a third articulation point. The basis appears subdivided by two longitudinal constrictions (from anterior over ventral to posterior) into three distinguishable portions: a medial, a central and a lateral portion. The medial portion (mBa in Fig. 13A–C) is fitted closely to the thoracic sternum (Fig. 13B, C) and carries an endite anteromedially that extends in a distomedial direction (Fig. 13A, B). Distally, the medial portion articulates via an anterior and a posterior articulation point (+ in Fig. 13A, B) with the endopod (i.e. the ischium). The constriction at the transition of the medial to the central portion forms a medial–central apodeme, serving as attachment site for one extrinsic exopod muscle (BEx1). The central and the lateral portions together form the distal (or ventral) wall of the basis (cBa and lBa in Fig. 13A, B). The proximal anterior margin of these portions forms a transversal invagination (aBa in Fig. 13A), serving as attachment site for two muscles (TB3 and BEx3). This invagination is most pronounced at its most medial and most lateral extent, respectively. The posterolateral margin of the lateral portion of the basis extends proximally towards the direction of the coxa, as a narrow cuticular beam; the basis and coxa are, in this area, separated by a wide interpodomeral membrane (Fig. 13B). Anterolaterally, the lateral portion of the basis curves proximolaterally, establishing a contact point (and possibly an articulation) with the epipod (Ep in Fig. 13A). Distolaterally within the membrane of the lateral portion of the basis, the exopod (Ex in Fig. 13A, B) articulates via an anterior and a posterior hinge point with the basis. The peduncle of the exopod comprises a short stem and a much longer distal portion, followed by a flagellum. The peduncle is broad and anteroposteriorly flattened, with a ventral bulge and a prominent distodorsal pointed protrusion. The peduncle articulates with the flagellum via an anteroventral articulation point. The cuticle of the first annulus is slightly more robust around this joint. All individuals examined exhibited a total of eight annuli (Fig. 13A). The crescent-shaped endopod consists of the ischium, merus, carpus, propodus and dactylus. Anteriorly, the endopod describes a strong concave curvature (Fig. 13A). The ischium (Is in Fig. 13A, B) is about as long as the proximodistal extent of the basis and carries medially a more or less distinct endite. A bicondylar articulation with the merus is realized by an anteromedial and a lateral articulation point, respectively (+ in Fig. 13A, B). The merus (Me in Fig. 13A, B) is about as long as the ischium and carries medially a more or less distinct endite. A bicondylar articulation with the carpus is formed by an inwardly folded posterior edge and an anterior articulation point (+ in Fig. 13A, B). The carpus (Ca in Fig. 13A, B) is about twice as long as the merus. A bicondylar articulation with the propodus is formed by an anterior and a posterior articulation point, respectively (+ in Fig. 13A, B). The propodus (Pr in Fig. 13A, B) is about half as long as the carpus. Its distal opening is not oriented distally but is ~90° displaced in a medial direction. A bicondylar articulation with the dactylus is formed by a medial and a lateral articulation point, respectively (+ in Fig. 13A, B). The dactylus is relatively short and rounded (Da in Fig. 13A, B), with its distal setose tip facing a proximomedial direction., Published as part of Grams, Markus, Klinger, Michael & Richter, Stefan, 2023, Neither leg nor jaw-nor always the same: a critical revision of the eumalacostracan maxilliped, pp. 965-1004 in Zoological Journal of the Linnean Society 197 (4) on pages 986-990, DOI: 10.1093/zoolinnean/zlac083, http://zenodo.org/record/7797605