| Eurotrochilus | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Clade: | Strisores |
| Order: | Apodiformes |
| Family: | Trochilidae |
| Genus: | †Eurotrochilus Mayr, 2004 |
| Type species | |
| E. inexpectatus[1] | |
| Species | |
Eurotrochilus is an extinct genus ofstem grouphummingbirds (Trochilidae) and are the closest known relatives of thecrown group Trochilidae.[3] DespiteEurotrochilus being morphologically very similar to modern hummingbirds, they still retained several primitive features and are not closely related to any specific extant hummingbird in the crown group.[4] There are currently two described species ofEurotrochilus:E. inexpectatus[1] andE. noniewiczi.[2]
Eurotrochilus has been dated back to theRupelian age of the earlyOligocene era, which occurred during thePaleogene period. While there is some debate over exactly whenEurotrochilus was present, the most recent estimate is suggested to be 28 to 34 million years ago.[2]
The discovery ofEurotrochilus fossils inGermany,France, andPoland was extremely important because today all 328 of theextant species of hummingbirds only occur in theNew World but the fossils ofEurotrochilus suggest anOld World origin.[5] Extant hummingbirds are distinctly different than all other avians because of their unique adaptations for hovering flight andnectarivory.[4] Like extant hummingbirds,Eurotrochilus has these adaptations and are the only genus of stem group Trochilidae to do so.[4]
The generic epithetEurotrochilus is derived from the location and family of the fossils found;Euro referring to Europe, the continent where theholotype specimen was found, andTrochilus referring to the type genus ofTrochilidae.[1] The specific epithet ofE. inexpectatus is Latin for "unexpected", indicative of the surprise felt by Gerald Mayr and his team when they discovered a modern-type fossil hummingbird in Europe.[1] The name of the second species,E. noniewiczi, refers to the surname of the private collector, Edward Noniewicza, who found the fossil specimen.[2]
Eurotrochilus specimens are some of the smallest fossil birds[1] and are referred to the order Apodiformes due to their strongly abbreviatedhumeri andulnae.[2] They are most similar to another early Oligocene member of the stem-group Trochilidae,Jungornis.[6] BothEurotrochilus andJungornis have morphological adaptations for sustained hovering flight, a characteristic of extant hummingbirds,[6] including the Apodiformsynapomorphy (abbreviated ulna and humerus) as well as pronounced distal protrusions on the humeral heads.[1] These adaptations inEurotrochilus are more pronounced though. Another difference is thatEurotrochilus have elongated beaks (unknown inJungornis[1]), which is evidence of nectarivory, the ability to consumenectar from flowers.Eurotrochilus are believed to be the first members of stem group Trochilidae to be able to perform nectarivory.
Eurotrochilus are more closely related to crown group Trochilidae than other members of stem group Trochilidae, likeJungornis, because of their specific adaptations for both nectarivory and hovering flight.
In some species ofEurotrochilus, the skull and beak have been roughly measured to be 34 millimeters.[2] The beaks ofEurotrochilus are greatly elongated, straight, and narrow, measuring from 15.5 to 20 millimeters in length, roughly 2.5 times as long as the cranium.[1][5] This beak shape is distinctly different than other known beak shapes of early Tertiary stem-group hummingbirds, which were short, wide, and most likely used for eating insects as opposed to nectar.[1]
The maxillary processes of the palatine bones in the beaks ofEurotrochilus are widely separated, indicating the presence ofrhynchokinesis, or the ability to flex the upper beak.[1] In addition,Eurotrochilus appear to have long nasal openings and largehyoid bones.[5] The large hyoid bones are thought to support a long protractile tongue, which extant hummingbirds use to lap up nectar.[5]
All of these adaptations made it possible forEurotrochilus to consume nectar from ornithophilous flowers, its main source of nutrients, and to pollinate these flowers as well.
Hummingbirds have specific morphological adaptations that enable them to fly forwards, backwards, sideways as well as hover for extended periods of time.[7] Hovering flight specifically is supported in Eurotrochilus by abbreviated ulnae and humeri and developed humeral protrusions.
The ulna ofEurotrochilus measures between 6.7 and 8.8 millimeters, which is shorter than the ulna ofJungornis, which measures 13 millimeters.[5] WhileJungornis andEurotrochilus both have abbreviated ulnas, the extreme abbreviation inEurotrochilus supports monophyly of theclade that includes onlyEurotrochilus and crown-group Trochilidae.[1] Another synapomorphy ofEurotrochilus and crown-group Trochilidae includes the presence of deepfossae, or depressions, on the caudal surface of the proximal end of the ulnae.[6]
The humeri ofEurotrochilus have been measured to be between 6.0 and 6.5 millimeters.[2] It is considered short and stout when compared to other Apodiformes, except extant hummingbirds. In addition, the humeri have a wide proximal articular part[2] and there are pronounced distal protrusions on the caput humeri, which is a synapomorphy ofJungornis,Eurotrochilus, and crown group Trochilidae.[6] The humeral protrusions inEurotrochilus are significantly more marked than inJungornis and are more similar to Trochilidae.[1] These morphological specializations of the humeri allow the bone to rotate during hovering flight.[4]
Additional adaptations present for hovering flight in both groups include curved and relatively short wings, square-shaped tails,[5] and a column-like sternal end of thecoracoid with a convex dorsal surface.[1]
Despite the similarities between the two, crown group Trochilidae has a more derived morphology thanEurotrochilus, showingEurotrochilus to be a stem group representative.[1] These more primitive morphologies inEurotrochilus include the bones of the hand (carpometacarpus and distalphalanges) being longer than the ulna, the carpometacarpus lacking a dentiform process, and the presence of a small intermetacarpal process.[1] Scientists are confident though with the assignment ofEurotrochilus to stem group Trochilidae as there has been no identification of derived characteristics that would causeEurotrochilus to be assigned to any other taxa of aves.[6]
SixEurotrochilus specimens have been identified in three countries of central Europe:Germany,France, andPoland. Two species have been identified,E. inexpectatus andE. noniewiczi.
Eurotrochilus was first described by Dr.Gerald Mayr in 2004 when he found two previously unidentified tiny bird skeletons in the drawers of the Stuttgart National History Museum.[4] The skeletons were from the former clay pit of the Bott-Eder GmbH ("Grube Unterfeld") inWiesloch-Frauenweiler of Southern Germany.[1] One partially disarticulated skeleton is theholotype for the speciesEurotrochilus inexpectatus and the other specimen consists of two slabs of a partially disarticulated skeleton.[1]
The discovery of the fossil hummingbirdEurotrochilus inexpectatus was a significant discovery because it provided the most convincing evidence for the presence of modern-looking hummingbirds of stem-group Trochilidae in the Old World.[1] Previously, the oldest fossil hummingbirds capable of hovering flight andnectarivory were modern hummingbirds estimated to be 10,000-30,000 years old from theQuaternary Period found in cave deposits of Central and South America.[4] While extant hummingbirds in crown-group Trochilidae most likely originated in the new world, the discovery ofEurotrochilus broadens the evolutionary history of modern hummingbirds.
In 2006, Dr. Gerald Mayr again described a previously unidentified specimen ofEurotrochilus inexpectatus from the same clay pit in Southern Germany. This specimen was found by Anette and Harald Oechsler in 1994 and was identified by Mayr as the second slab of theEurotrochilus inexpectatus holotype.[6] Also, Mayr described another skeleton from the same area that included the skull, some vertebrae, part of the pectoral girdle, and an incomplete left wing that was found by several students in 2005.[6]
In 2007, Dr. Antoine Louchart described a specimen found in the Le Grand Banc Strata in southeastern France that consisted of an almost complete skeleton on a slab. The skeleton is in ventral view with the head in left lateral view.[5] This specimen is unique because it preserves almost the complete skeleton, and also a thin layer of dark organic matter preserved the complete feathering pattern of the bird.[5] The specimen had all of thesynapomorphies and adaptations identified inE. inexpectatus but Louchart could not identify the specimen asE. inexpectatus because of differences in lengths of several bones including phalanges of wings and lateral process ofcoracoid.[5] He did note though that the differences could be attributed to either sexual or individual distinctness, rather than speciation.[5]
TheEurotrochilus sp. specimen found in France not only revealed more characteristics of the genusEurotrochilus but also extended the known geographical distribution ofEurotrochilus.
The geographical distribution ofEurotrochilus was extended even further in 2007 when Dr. Zygmunt Bochenski and Dr. Zbigniew M. Bochenski described another specimen atWinnica, Świętokrzyskie Voivodeship, east ofJaslo in Southeastern Poland in theMenilite formation.[2] The specimen was a slab and counter slab of a near-complete skeleton formerly kept in the private collection of Edward Noniewicz. The specimen is the holotype for a new species ofEurotrochilus,E. noniewiczi. The specimen had all of the same characteristics ofE. inexpectatus but also had unique proportions of bones, a coracoid that widens near the sternal end, and a distinctly smaller ulna and humerus compared toE. inexpectatus and Louchart'sEurotrochilus specimen, prompting the description of a new species.[2]
In 2009, Harald and Annette Oechsler found the fourth specimen ofEurotrochilus inexpectatus in the former clay pit of the Bott-Eder GmbH ("Grube Unterfeld") inWiesloch-Frauenweiler of Southern Germany. Mayr described the jumbled but closely associated specimen in 2010. It offered insight into previously unknown osteological features including a developedprocessus intermetacaroalis and the presence ofcrista deltopectoralis on the humerus.[8]
Thepaleoenvironment ofEurotrochilus species occurred during theRupelian age of the earlyOligocene era. All of the specimens ofEurotrochilus found throughout Central Europe seem to agree with this geological era: German specimens are estimated to be 32 million years old,[1][6] the French specimen is estimated to be 28-34 million years old,[5] and Polish specimens are estimated to be 31 million years old.[2]
During the Oligocene era, theParatethys Ocean covered the majority of Central and Eastern Europe.[9] The Winnica site in Poland where theE. noniewiczi specimen was found used to be submerged in the Paratethys Ocean.[9] The Winnica site produced a large diversity of bird remains, aquatic and terrestrial, which indicates that there was most likely a coastal or shoreline climate with richavifauna present.[9]E. inexpectatus and a large diversity of other avian specimens from clay pits in Southern Germany were also found inmarine sediment, supporting the theory that the majority of Central Europe most likely had a marine/coastal ecosystem.[10]
Based on the other species found alongside all theEurotrochilus specimens, the local climate is believed to have been sub-tropical to tropical.[5] The warm, frost-free climate would have supported broad-leaved evergreen forests as well as palm-rich coastal forests on sandy soils.[10] It is difficult to estimate the winter conditions during this period without knowing the migratory habits of the avian species but based on their fruit and nectar diets, scientists believe that this area of Europe most likely experienced mild winters.[10]
_(19840424759).jpg)
Ornithophilous flowers, or flowers pollinated by birds, are present in theOld World. Flowers likeCanarina eminii (Campanulacea),Impatiens sakeriana (Balasaminaceae), andAgapetes spp (Ericaceae) are similar in morphology to flowers with nectar from the New World and they specifically lack a perch for birds.[1] In the New World, similar flowers are pollinated by modern hummingbirds that do not need to perch on flowers due to their adaptation for hovering flight.[1] Modern hummingbirds are not present in the Old World and instead long-tongued bees pollinate these flowers.[7]
Considering thatEurotrochilus had long beaks and tongues to consume nectar as well as the ability to hover while in flight, it seems plausible to conclude that ornithophilous flowers in the Old World evolved bird-pollination morphologies in response toEurotrochilus.[7] If this were true, then it would suggest a maximum age for hummingbird-pollinated plants (i.e. nectivorous plants) as these plants would not be able to be pollinated before the early Oligocene withoutEurotrochilus.[1]
The abundance ofE. inexpectatus specimens at the Frauenweiler site in Southern Germany suggests thatEurotrochilus were possibly locally abundant during the early Oligocene, making them the most likely dominant pollinators of ornithophilous flowers.[6] Ecological competition with long-tongued bees for ornithophilous flowers is a suggested explanation for the extinction ofEurotrochilus and modern hummingbirds in Europe.[6] Another possible explanation for their extinction is rapid climate change from the suspected moderate tropical climate, which would have been a critical problem considering the small size ofEurotrochilus.[10]
| |||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||
