Die Raninidae sind eine Familie ursprünglicher Krabben (Brachyura). Anders als bei den meisten anderen Krabben ist das stark verkleinerte Abdomen nicht unter den Cephalothorax geklappt. Die Scherenbeine der Raninidae und die vorderen drei Laufbeinpaare haben sich zu Grabwerkzeugen entwickelt, mit denen sich die Tiere in den Sand eingraben.
Es gibt über 30 rezente Arten die alle im Sand an tropischen Meeresküsten leben.
Die Raninidae sind fossil seit der Unteren Kreidezeit bekannt. Im Tertiär waren sie sehr häufig.
In der Familie werden 46 rezente und 183 ausgestorbene Arten in 34 Gattungen und sieben Unterfamilien registriert:
Die Raninidae sind eine Familie ursprünglicher Krabben (Brachyura). Anders als bei den meisten anderen Krabben ist das stark verkleinerte Abdomen nicht unter den Cephalothorax geklappt. Die Scherenbeine der Raninidae und die vorderen drei Laufbeinpaare haben sich zu Grabwerkzeugen entwickelt, mit denen sich die Tiere in den Sand eingraben.
Es gibt über 30 rezente Arten die alle im Sand an tropischen Meeresküsten leben.
Die Raninidae sind fossil seit der Unteren Kreidezeit bekannt. Im Tertiär waren sie sehr häufig.
Raninidae is a family of unusual crabs, sometimes known as "frog crabs", on account of their frog-like appearance. They are taken by most scientists to be quite primitive among the true crabs. They closely resemble the (unrelated) mole crabs, due to parallel evolution or convergent evolution. In both groups, the claws are modified into tools for digging, and the body is a rounded shape that is easy to bury in sand. Unlike most other true crabs, the abdomens of raninids are not curled under the cephalothorax.
They spend most of their time buried in the sand with their eyes popping out so they can grab unaware prey. They also emerge for mating.[1] Raninids are omnivores and some have been found to have consumed Sardinella, crab, shrimp, bivalve, ray, hydroid, copepod, and squid.[2]
The earliest fossil attributable to the family Raninidae dates from the Albian.[3]
Raninids dorsal surfaces have varying textures; smooth, pitted, granular, inclined or fungiform nodes, eroded, scabrous or terraced. Raninids have a strongly specialized respiratory mechanism, they lack Milne-Edwards openings and have modified antennae which they inhale through and they generally have posterior branchial orifices. They have eight pairs of vertically arranged gills all of which are functional. Their abdomens are short, incompletely folded, and have six freely articulated somites and a small telson. Raninids also lack a sterno-abdominal cavity.[4]
Frog crabs are marine animals and depending on the species they can be found at varying depths, members of this family have been found to live at depths ranging anywhere from 1m to over 900m.[5] The 46 species are distributed across pan-tropical regions with certain regions having many species and some with only one. Some species are found across various regions while others can only be found in one specific region.[6]
Sexual dimorphism is seen in both extant and extinct members of this family. Sexually dimorphic characteristics of the abdomen are seen throughout the family, though throughout the subfamilies there are varying styles and degrees of development.[7]
Some other sexually dimorphic characteristics include males being larger, having more developed anterolateral carapace teeth, larger chelae, and different setae on the P1 propodus and dactylus as compared to those of the females.[1]
Unlike other Podotremate, Raninids’ spermatheca opens anteriorly on sternite 7 rather than at the extremities of sternal suture 7/8. The formation of the spermathecal chamber, which doesn’t differ much from the usual popdptreme configuration, is done by the separation of the two laminae which compose endosternite 7/8. In all raninoids, spermathecal apertures are close to each other, separated by medial line, recessed in medial depression, and located in proximity to the female gonopore. Female gonopores are found on P3 coxae and male gonopores on P5 coxae. There is a variety in shapes when it comes to the male sexual gonopods showing strong diversity. In reproduction sperm is ejaculated to the base of the G1 it is then picked up by the spoon-like G2 and placed in the distal portion of the G1, it is then transferred through the G1 ejaculatory channel into the spermatheca.[1]
The taxonomic status of Raninidae has varied greatly with academics citing various information learned about them to try and discern where they belong. Where these creatures fit evolutionarily has been a topic of debate and study ever since the 18th century. Their status varying so much over the years can in part be attributed to the unusual characteristics of raninids. Even to this day there are still ongoing debates surrounding the raninoid lineage.[1]
The 46 extant and 183 extinct species in the famila Raninidae are arranged among 34 genera in 7 subfamilies:[8]
Raninidae is a family of unusual crabs, sometimes known as "frog crabs", on account of their frog-like appearance. They are taken by most scientists to be quite primitive among the true crabs. They closely resemble the (unrelated) mole crabs, due to parallel evolution or convergent evolution. In both groups, the claws are modified into tools for digging, and the body is a rounded shape that is easy to bury in sand. Unlike most other true crabs, the abdomens of raninids are not curled under the cephalothorax.
They spend most of their time buried in the sand with their eyes popping out so they can grab unaware prey. They also emerge for mating. Raninids are omnivores and some have been found to have consumed Sardinella, crab, shrimp, bivalve, ray, hydroid, copepod, and squid.
The earliest fossil attributable to the family Raninidae dates from the Albian.
Les Raninidae sont une famille de crabes. Elle comprend près de cinquante espèces actuelles et près de 200 fossiles dans 34 genres dont 22 fossiles.
Cyrtorhininae Guinot, 1993
Lyreidinae Guinot, 1993
Notopodinae Serène & Umali, 1970
Ranininae De Haan, 1839
Raninoidinae Lőrenthey in Lőrenthey & Beurlen, 1929
Symethinae Goeke, 1981
†Palaeocorystinae Lőrenthey in Lőrenthey & Beurlen, 1929
Sous-famille indéterminée
Les Raninidae sont une famille de crabes. Elle comprend près de cinquante espèces actuelles et près de 200 fossiles dans 34 genres dont 22 fossiles.
Raninidae is een familie van de sectie Raninoida uit de infraorde krabben en omvat volgende onderfamilies: [2]
Raninidae is een familie van de sectie Raninoida uit de infraorde krabben en omvat volgende onderfamilies:
Cyrtorhininae Guinot, 1993 Lyreidinae Guinot, 1993 Notopodinae Serène & Umali, 1970 Ranininae De Haan, 1839 Raninoidinae Lőrenthey, 1929 Symethinae Goeke, 1981Raninidae là một họ cua, được xem là một họ "cua thực sự" tương đối nguyên thủy. Chúng có bề ngoài làm liên tưởng đến Hippoidea, nhưng điều này là do tiến hóa song song hoặc tiến hóa hội tụ. Ở cả hai nhóm, càng trở thành một công cụ để đào bới, và cơ thể tiến hóa thành hình dạng để có thể vùi mình trong cát.
Những hóa thạch cổ nhất của Raninidae có niên đại từ tầng Alba.[1]
46 loài còn tồn tại và 183 loài đã tuyệt chủng trong họ Raninidae được xếp vào 34 chi và 7 phân họ:[2]
Raninidae là một họ cua, được xem là một họ "cua thực sự" tương đối nguyên thủy. Chúng có bề ngoài làm liên tưởng đến Hippoidea, nhưng điều này là do tiến hóa song song hoặc tiến hóa hội tụ. Ở cả hai nhóm, càng trở thành một công cụ để đào bới, và cơ thể tiến hóa thành hình dạng để có thể vùi mình trong cát.
Những hóa thạch cổ nhất của Raninidae có niên đại từ tầng Alba.
蛙蟹科（學名：Raninidae）是螃蟹的其中一個科，模式屬是蛙形蟹。
根據現存的化石紀錄，蛙蟹科生物最早期的化石於早白堊紀的阿爾布階出現[1]。
常見的蛙蟹科生物有：
蛙蟹科的外形獨特，就好像蛙類一樣，而且在科學家來說，蛙蟹科生物的外型亦比真蟹派物種的外型原始（英语：Primitive (phylogenetics)）。其型態與異尾下目的蟬蟹總科物種非常相似，儘管兩種物種並沒有關連，而只是因為平行演化或趨同演化：這兩組物種的螯都已演化成為用於挖掘的工具，而牠們的身體也演變成圓圓的，易於埋在沙子中的。與大多數其他真蟹派物種不同的，是蛙蟹科物種的腹部並不捲曲到其頭胸部之下。
蛙蟹科有46個現生種及183個化石種，分佈於七個亞科34個屬之內[2]：
