Fig 1.
Specimens with branchial swellings.
All scale bars are 1cm. Red arrows indicate swellings. A-C) Modern specimens of Munida valida TAMU cat. no. 2–3061 (A,C), 2–3063 (B). (D-F) Fossil specimens of Macroacaena rosenkrantzi NHMD MGUH 34322 (D), MGUH 34323 (E), MGUH 34324 (F). G) Fossil specimen of Panopeus nanus UF 288470.
Fig 2.
Finite element model of Macroacaena rosenkrantzi with constraints in FreeCAD.
Red arrows indicate applied forces.
Fig 3.
All specimens are shown in transverse cross-section. Scale bars are 1 cm, shown to the right of each specimen. Red arrows indicate swellings. A-C) Modern specimens of Munida valida TAMU cat. no. 2–3061 (A,C), 2–3063 (B). D-F) Fossil specimens of Macroacaena rosenkrantzi NHMD MGUH 34322 (D), MGUH 34323 (E), MGUH 34324 (F). G) Fossil specimen of Panopeus nanus UF 288470.
Fig 4.
Swellings are displayed to the right and circled in red for each specimen. Values on scales are in pascals (Pa). A-C) Modern specimens of Munida valida TAMU cat. no. 2–3061 (A,C), 2–3063 (B). D-F) Fossil specimens of Macroacaena rosenkrantzi NHMD MGUH 34322 (D), MGUH 34323 (E), MGUH 34324 (F). G) Fossil specimen of Panopeus nanus UF 288470.
Fig 5.
Histograms of model vertex von Mises stress values exceeding 5 MPa.
Red lines indicate the median stress values. Blue lines indicate the mean stress values. The number of vertices exceeding 5MPa is given for each side of each specimen. A) Munida valida specimen A TAMU cat. no. 2–3061. B) M. valida specimen B TAMU cat. No. 2–3063. C) M. valida specimen C TAMU cat. no. 2–3061. D) Macroacaena rosenkrantzi specimen A NHMD MGUH 34322. E) M. rosenkrantzi specimen B NHMD MGUH 34323. F) M. rosenkrantzi specimen C NHMD MGUH 34324. G) Panopeus nanus UF 288470.
Table 1.
Summary of von Mises stress values from specimen FEA.