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Rhamphorhynchus (animal)
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Rhamphorhynchus , "beak snout", is a genus of long-tailed pterosaurs in the Jurassic period. Less specialized than contemporary, short-tailed pterodactyloid pterosaurs such as Pterodactylus, it had a long tail, stiffened with ligaments, which ended in a characteristic diamond-shaped vane. The jaws of Rhamphorhynchus housed needle-like teeth, which were angled forward, with a curved, sharp, beak-like tip lacking teeth, indicating a diet mainly of fish and insects.
Although fragmentary fossil remains possibly belonging to Rhamphorhynchus have been found in England, Tanzania, and Spain, the best preserved come from the Solnhofen limestone of Bavaria, Germany.
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Encyclopedia
Rhamphorhynchus , "beak snout", is a genus of long-tailed pterosaurs in the Jurassic period. Less specialized than contemporary, short-tailed pterodactyloid pterosaurs such as Pterodactylus, it had a long tail, stiffened with ligaments, which ended in a characteristic diamond-shaped vane. The jaws of Rhamphorhynchus housed needle-like teeth, which were angled forward, with a curved, sharp, beak-like tip lacking teeth, indicating a diet mainly of fish and insects.
Although fragmentary fossil remains possibly belonging to Rhamphorhynchus have been found in England, Tanzania, and Spain, the best preserved come from the Solnhofen limestone of Bavaria, Germany. Many of these fossils preserve not only the bones but impressions of soft tissues such as wing membranes. Scattered teeth believed to belong to Rhamphorhynchus have been found in Portugal as well.
Description
The largest known specimen of Rhamphorhynchus muensteri (catalog number BMNH 37002) measures 1.26 meters (4.1 ft) long with a wingspan of 1.81 m (5.9 ft).
Skull
Contrary to a 1927 report by pterosaur researcher Broili, Rhamphorhynchus lacked any bony or soft tissue crest, as seen in several species of contemporary small pterodactyloid pterosaurs. Broili claimed to have found a 2 millimeter tall crest made of thin bone that ran much of the skulls length in one Rhamphorhynchus specimen, evidenced by an impression in the surrounding rock and a few small fragments of the crest itself. However, subsequent examination of this specimen by Wellnhofer in 1975 and Bennett in 2002 using both visible and ultraviolet light found no trace of a crest, and both concluded that Broili was mistaken. The supposed crest, they concluded, was simply an artifact of preservation.
The teeth of Rhamphorhynchus intermesh when the jaw is closed and are suggestive of a piscivorous diet. There are 20 teeth in the upper jaw and 14 in the lower jaw.
History and classification
The classification and taxonomy of Rhamphorhynchus, like many pterosaur species known since the Victorian era, is complex, with a long history of reclassification under a variety of names, often for the same specimens.
The original type specimen of Rhamphorhynchus was first described in 1830 by Georg zu Münster. Like many pterosaurs described in the mid 19th century, Rhamphorhynchus was originally considered to be a species of Pterodactylus. However, at the time, many scientists incorrectly considered Ornithocephalus to be the valid name for Pterodactylus. What would become the type specimen of Rhamphorhynchus was therefore originally named Ornithocephalus münsteri by Georg August Goldfuss in a 1831 follow-up to Münster's short paper. Note that the ICZN later ruled that non-standard Latin characters such as ü would not be allowed in scientific names, and the spelling münsteri was emended to muensteri by Richard Lydekker in 1888.
In 1839, Münster described another specimen he considered to belong to Ornithocephalus (i.e. Pterodactylus), with a distinctive long tail. He named it Ornithocephalus longicaudus, meaning "long tail", to differentiate it from the specimens with short tails (the true specimens of Pterodactylus).
In 1845, Hermann von Meyer officially emended the original species Ornithocephalus münsteri to its correct name, Pterodactylus münsteri, since the name Pterodactylus had been by that point recognized as having priority over Ornithocephalus. In a subsequent 1846 paper describing a new species of long-tailed 'pterodactyl', von Meyer decided that the long-tailed forms of Pterodactylus were different enough from the short-tailed forms to warrant placement in a subgenus, and he named his new species Pterodactylus (Rhamphorhynchus) gemmingi. It was not until 1847 that von Meyer elevated Rhamphorhynchus to a full-fledged genus, and officially included in it both long-tailed species of Pterodactylus known at the time, R. longicaudus (the original species preserving a long tail) and R. gemmingi.
The original species, Pterodactylus muensteri, remained misclassified until a re-evaluation was published by Richard Owen in an 1861 book. Because the type species of newly reclassified Rhamphorhynchus münsteri had been published before the first recognized long tiled form actually named Rhamphorhynchus (R. longicaudus), R. muensteri was now the type species for the entire genus.
The type specimen of R. muensteri, described by Münster and Goldfuss, was lost during World War II. If available, a new specimen is designated the type (neotype) if the original is lost or deemed too poorly preserved. Peter Wellnhofer declined to designate a neotype in his 1975 review of the genus, because a number of high quality casts of the original specimen were still available in museum collections.
By the 1990s (and following Wellnfofer's consolidation of many previously named species), about five species of Rhamphorhynchus were recognized from the Solnhofen limestone of Germany, with a few others having been named from Africa, Spain, and the UK based on fragmentary remains. Most of the Solnhofen species were differentiated based on their relative size, and size-related features such as relative length of the skull.
In 1995, pteorsaur researcher Chris Bennett published an extensive review of the currently recognized German species. Bennett concluded that all the supposedly distinct German species were actually different year-classes of a single species, R. muensteri, representing distinct age groups, with the smaller species being juveniles and the larger adults. Bennett's paper did not cover the British and African species, though he suggested these should be considered indeterminate members of the family Rhamphorhynchidae and not necissarily species of Rhamphorhynchus itself.
Paleobiology
Life history
Traditionally, the large size variation between specimens of Rhamphorhynchus has been taken to represent species variation. However, in a 1995 paper, Bennett argued that these "species" actually represent year-classes of a single species, Rhamphorhynchus muensteri, from fledglings to adults. Following from this interpretation, Bennett found several notable changes that occurred in R. muensteri as the animal aged.
Juvenile Rhamphorhynchus had relatively short skulls with large eyes, and the toothless beak-like tips of the jaws were shorter in juveniles than adults, with rounded, blunt lower jaw tips eventually becoming slender and pointed as the animals grew. Adult Rhamphorhynchus also developed a strong upward "hook" at the end of the lower jaw. The number of teeth remained constant from juvenile to adult, though the teeth became relatively shorter and stockier as the animals grew, possibly to accommodate larger and more powerful prey. The pelvic and pectoral girdles fused as the animals aged, with full pectoral fusion attained by one year of age.
The shape of the tail vane also changed across various age classes of Rhamphorhynchus. In juveniles, the vane was shallow relative to the tail and roughly oval, or "lancet-shaped". As growth progressed, the tail vane became diamond-shaped, and finally triangular in the largest individuals.
The smallest known Rhamphorhynchus specimen has a wingspan of only 290 millimeters; however, it is likely that even such a small individual was capable of flight. Bennett examined two possibilities for hatchlings: that they were altricial, requiring some period of parental care before leaving the nest, or that they were precocial, hatching with sufficient size and ability for flight. If precocious, Bennett suggested that clutches would be small, with only one or two eggs laid per clutch, to compensate for the relatively large size of the hatchings. Bennett did not speculate on which possibility was more likely, though the discovery of a pterosaur embryo (Avgodectes) with strongly ossified bones suggests that pterosaurs in general were precocial, able to fly soon after hatching with minimal parental care.
Metabolism
Having determined that Rhamphorhynchus specimens fit into discrete year-classes, Bennett was able to estimate growth rate during one year by comparing the size of one-year-old specimens with two-year-old specimens. He found that the average growth rate during the first year of life for Rhamphorhynchus was 130% to 173%, slightly faster than the growth rate in alligators. Growth likely slowed considerably after sexual maturity, so it would have taken more than three years to attain maximum adult size.
This growth rate is much slower than the rate seen in large pterodactyloid pterosaurs such as Pteranodon, which attained near-adult size within the first year of life. Additionally, pterodactyloids had determinate growth, meaning that the animals reached a fixed maximum adult size and stopped growing. Previous assumptions of rapid growth rate in rhamphorhynchoids were based on the assumption that they needed to be warm-blooded to sustain active flight. Warm-blooded animals, like modern birds and bats, normally show rapid growth to adult size and determinate growth. However, there is no evidence for either in Rhamphorhynchus, and Bennett considered his findings consistent with an ectothermic metabolism, though he recommended more studies needed to be done. Cold-blooded Rhamphorhynchus, Bennett suggested, may have basked in the sun or worked their muscles to accumulate enough energy for bouts of flight, and cooled to ambient temperature when not active to save energy, like modern reptiles.
Sexual dimorphism
Both Koh and Wellnhofer recognized two distinct groups among adult Rhamphorhynchus muensteri, differentiated by the proportions of the neck, wing, and hind limbs, but particularly in the ratio of skull to humerus length. Both researchers noted that these two groups of specimens were found in roughly a 1:1 ratio, and interpreted them as different sexes. Bennett tested for sexual dimorphism in Rhamphorhynchus by using a statistical analysis, and found that the specimens did indeed group together into small-headed and large-headed sets. However, without any known variation in the actual form of the bones or soft tissue (morphological differences), he found the case for sexual dimorphism inconclusive.
Head orientation
In 2003, a team of researchers lead by Lawrence Witmer studied the brain anatomy of several types of pterosaurs, including Rhamphorhynchus muensteri, using endocasts of the brain they retrieved by performing CAT scans of fossil skulls. Using comparisons to modern animals, they were able to estimate various physical attributes of pterosaurs, including relative head orientation during flight and coordination of the wing membrane muscles. Witmer and his team found that Rhamphorhynchus held its head parallel to the ground due to the orientation of the osseous labyrinth of the inner ear, which helps animals detect balance. In contrast, pterodactyloid pterosaurs such as Anhanguera appear to have normally held their heads at a downward angle, both in flight and while on the ground.
Species
A large number of Rhamphorhynchus species have been named, but are currently considered year-classes of R. muensteri by most researchers. Currently recognized specimens of Rhamphorhynchus have previously been published on under the following junior synonyms: The species R. jessoni was recovered from the Huntingdonshire clay in England.
Note that Rhamphorhynchus is also a genus of orchid, named in 1977 by botanist L.A. Garay. In biological nomenclature, the same name may be used for an animal that has already been used for a plant or vice versa.
Synonyms
Synonyms of Rhamphorhynchus muensteri:
- Ornithocephalus muensteri Goldfuss, 1831 emend. Lydekker, 1888
- Pterodactylus muensteri Goldfuss, 1831 emend. Lydekker, 1888
- Pterodactylus (Rhamphorhynchus) muensteri (Goldfuss, 1831)
- R. longicaudus (Münster, 1839) von Meyer, 1846
- Pterodactylus longicaudus Münster, 1839
- Odontorhynchus longicaudus (Münster, 1839) Olshevsky, 1978
- Ornithocephalus longicaudus (Münster, 1839) Wagner, 1851
- Rhamphorhynchus (Odontorhynchus) longicaudus (Münster, 1839) Stolley, 1936
- R. gemmingi (von Meyer, 1846) von Meyer, 1855
- Pterodactylus gemmingi von Meyer, 1846
- Pterodactylus (Rhamphorhynchus) gemmingi von Meyer, 1846
- Ornithocephalus gemmingi (von Meyer, 1846) Wagner, 1851
- Rhamphorhynchus (Pterodactylus) gemmingi (von Meyer, 1846) von Meyer, 1855
- Pterodactylus lavateri von Meyer, 1838
- Ornithopterus lavateri (von Meyer, 1838) von Meyer, 1860
- Pterodactylus (Ornithopterus) lavateri (von Meyer, 1838) Owen, 1851
- R. suevicus O. Fraas, 1855
- Pterodactylus hirundinaceus Wagner, 1857
- Pterodactylus (Rhamphorhynchus) hirundinaceus Wagner, 1857
- R. hirundinaceus (Wagner, 1857) Wagner, 1858
- R. curtimanus Wagner, 1858
- R. longimanus Wagner, 1858
- R. meyeri Owen, 1870
- R. phyllurus Marsh, 1882
- Pteromonodactylus phyllurus (Marsh, 1882) Teriaev, 1967
- R. longiceps Woodward, 1902
- Ornithocephalus giganteus Oken, 1819
- Pterodactylus giganteus (Oken, 1819)
- Pterodactylus grandis Cuvier, 1824
- Ornithocephalus grandis (Cuvier, 1824) Wagner, 1851
- R. grandis (Cuvier, 1824) Lydekker, 1888
- Pterodactylus secundarius von Meyer, 1843
- Ornithocephalus secundarius (von Meyer, 1843) Wagner, 1851
- R. kokeni F. Plieninger, 1907
- R. megadactylus von Koenigswald, 1931
- R. carnegiei Koh, 1937
Dubious species
Dubious species of Rhamphorhynchus:
- R. jessoni (Lydekker, 1890)
- R. tendagurensis (Peck, 1931)
- R. intermedius Koh, 1937
- R. intermedius var. brevialata Koh, 1937
"Odontorhynchus"
"Odontorhynchus" aculeatus was based on a skull with lower jaw that is now lost. This set of jaws supposedly differed in having two teeth united at the tip of the lower jaw, and none at the tip of the upper jaw. The skull was 6.5-7.0 cm (2.56-2.76 in), making it a small form. Stolley, who described the specimen in 1936, argued that R. longicaudus also should be reclassified in the genus "Odontorhynchus". Both Koh and Wellnhofer rejected this idea, arguing instead that "Odontorhynchus" was a junior synonym of R. longicaudus. Bennett agreed with their assessments, and included both "Odontorhynchus" and R. longicaudus as synonyms of R. muensteri.
In popular culture
Rhamphorhynchus was featured in the third episode "Cruel Sea" of the award winning Walking with Dinosaurs television series. The reptile is shown living amongst the seaside hunting fish, digging for horseshoe crab eggs and stripping bark off conifer trees to find bark beetle larvae. It is also shown being hunted by Eustreptospondylus.
It also appeared in the 1971 film When Dinosaurs Ruled the Earth. In the 1977 Japanese monster movie Legend of Dinosaurs and Monster Birds, a plesiosaur and an oversized Rhamphorhynchus terrorize the people around Mt. Fuji until they meet and do battle to the death amidst a volcanic eruption. In The Land Before Time VII there is a sinister Rhamphorhynchus named Rinkus.
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