fishes Archivi - Scientificult

Biology

Vocal Communication Originated over 400 Million Years Ago

By ScientifiCult 26 October 2022

Vocal Communication Originated over 400 Million Years Ago

Acoustic communication is not only widespread in land vertebrates like birds and mammals, but also in reptiles, amphibians and fishes. Many of them are usually considered mute, but in fact show broad and complex acoustic repertoires. According to researchers at the University of Zurich, the evolutionary origin of vocal communication dates back more than 400 million years.

The use of vocalizations as a resource for communication is common among several groups of vertebrates: singing birds, croacking frogs or barking dogs are some well-known examples. These vocalizations play a fundamental role in parental care, mate attraction and various other behaviors. Despite its importance, little is known about when and at what stage in the evolutionary history of vertebrates this behavior first appeared. Comparative analyses can provide insights into the evolutionary origin of acoustic communication, but they are often plagued by missing information from key groups that have not been broadly studied.

Acoustic abilities are widespread in land vertebrates

An international research team led by the University of Zurich (UZH) has therefore focused on species that have never been accessed before. Their study includes evidence for 53 species of four major clades of land vertebrates – turtles, tuataras, caecilians and lungfishes – in the form of vocal recordings and contextual behavioral information accompanying sound production.

“This, along with a broad literature-based dataset including 1800 different species covering the entire spectrum shows that vocal communication is not only widespread in land vertebrates, but also evidence acoustic abilities in several groups previously considered non-vocal,” says first author Gabriel Jorgewich-Cohen, PhD student at the Paleontological Institute and Museum of UZH.

Many turtles, for example, which were thought to be mute are in fact showing broad and complex acoustic repertoires.

Vocal Communication Originated over 400 Million Years Ago. The researchers were even able to detect acoustic communication in lungfish. (Image: Rafael C.B. Paradero)

Last common ancestor lived about 407 million years ago

To investigate the evolutionary origins of acoustic communication in vertebrates, the researchers combined relevant data on the vocalization abilities of species like lizards, snakes, salamanders, amphibians and dipnoi with phylogenetic trait reconstruction methods. Combined with data of well-known acoustic clades like mammals, birds, and frogs, the researchers were able to map vocal communication in the vertebrate tree of life.

“We were able to reconstruct acoustic communication as a shared trait among these animals, which is at least as old as their last common ancestor that lived approximately 407 million years before present,” explains Marcelo Sánchez, who led the study.

Acoustic communication did not evolve multiple times

So far, the scientific consensus favored a convergent origin of acoustic communication among vertebrates since the morphology in hearing apparatus and its sensitivity as well as the vocal tract morphology vary considerably among vertebrates. But according to the UZH researchers, the available evidence for this hypothesis lacks relevant data from key species so far considered non-vocal or neglected.

“Our results now show that acoustic communication did not evolve multiple times in diverse clades, but has a common and ancient evolutionary origin,” concludes Sánchez.

Literature:

Gabriel Jorgewich-Cohen, Simon William Townsend, Linilson Rodrigues Padovese, et al. Common evolutionary origin of acoustic communication in choanate vertebrates, Nature Communications, 25 October 2022. DOI: 10.1038/s41467-022-33741-8

Press release from the University of Zurich

Keep Reading

Biology

Fish fossils of Tujiaaspis vividus breathe new life into fin and limb evolutionary hypothesis

By ScientifiCult 29 September 2022

Fish Fossils of Tujiaaspis vividus Breathe New Life into Fin and Limb Evolutionary Hypothesis

A trove of fossils, unearthed in rock from China dating back some 436 million years, has revealed for the first time that the mysterious galeaspids, members of an extinct clade of jawless fish, possessed paired fins.

The discovery, by an international team led by Prof. ZHU Min from the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) of the Chinese Academy of Sciences and Prof. Philip Donoghue from the University of Bristol, shows the primitive condition of paired fins before they separated into pectoral and pelvic fins, the forerunner of arms and legs.

The findings were published in Nature on Sept. 28.

Fish fossils of Tujiaaspis vividus breathe new life into fin and limb evolutionary hypothesis. Fig. 1 Life reconstructions of Tujiaaspis vividus (Image by ZHENG Qiuyang)

Until now, the only surviving galeaspid fossils were heads, but these new fossils comprise whole bodies. They were found in rocks in Hunan Province and Chongqing and were named Tujiaaspis after the indigenous Tujia people who live in the region.

Fig. 3 The holotype specimen and its interpretative drawing of Tujiaaspis vividus from 436 million years old rocks of Chongqing, China (Image by Gai, et al.)

Theories abound about the evolutionary beginnings of vertebrate fins and limbs—the evolutionary precursors of arms and legs—and are mostly based on comparative embryology. There is a rich fossil record of early vertebrate , but they either had separated paired fins or they didn’t. There has been little evidence for the gradual evolution of fins.

According to first author GAI Zhikun, a professor at IVPP, “The anatomy of galeaspids has been something of a mystery since they were first discovered more than half a century ago. Tens of thousands of fossils are known from China and Vietnam, but almost all of them are just heads—nothing has been known about the rest of their bodies—until now.”

The new fossils are spectacular, preserving the whole body for the first time and revealing that these animals possessed paired fins that extended all the way from the back of the head to the very tip of the tail. This is a great surprise since scientists had thought galeaspids lack paired fins altogether.

“Tujiaaspis breathes new life into a century old hypothesis for the evolution of paired fins, through differentiation of pectoral (arms) and pelvic (legs) fins over evolutionary time from a continuous head-to-tail fin precursor,” said corresponding author Prof. Donoghue.

This “fin-fold” hypothesis has been very popular, but it has lacked any supporting evidence until now. The discovery of Tujiaaspis resurrects the fin-fold hypothesis and reconciles it with contemporary data on genetic control of the embryonic development of fins in living vertebrates.

Tujiaaspis shows the “primitive condition” for the evolution of paired fins, according to Prof. ZHU, who said that later jawless fish showed the first evidence for the separation of this fin-fold into pectoral and pelvic fins. Prof. ZHU also noted that the vestiges of elongate fin-folds could be seen in the embryos of living jawed fishes, which could be manipulated to produce them.

Fig. 2 3D reconstruction of Tujiaaspis vividus (Image by YANG Dinghua)

Bristol’s Dr. Humberto Ferron, a co-author, used computational engineering approaches to simulate the behaviour of models of Tujiaaspis with and without the paired fins. He said,

“The paired fins of Tujiaaspis act as hydrofoils, passively generating lift for the fish without any muscular input from the fins themselves. The lateral fin-folds of Tujiaaspis allowed it to swim more efficiently.”

“Our new analyses suggest that the ancestor of jawed vertebrates likely possessed paired fin-folds, which became separated into pectoral and pelvic regions,” said co-author Dr. Joseph Keating from the University of Bristol.

He noted that the primitive fins evolved musculature and skeletal support that allowed our fish ancestor to better steer their swimming and add propulsion.

“It is amazing to think that the evolutionary innovations seen in Tujiaaspis underpin locomotion in animals as diverse as birds, whales, bats, and humans,” he said.

Press release from the Chinese Academy of Sciences

Keep Reading

Biology

Fanjingshania renovata, Ancient ‘Shark’ from China Is Humans’ Oldest Jawed Ancestor

By ScientifiCult 29 September 2022

Fanjingshania renovata, an Ancient ‘Shark’ from China Is Humans’ Oldest Jawed Ancestor

Palaeontologists discover a 439-million-year-old ‘shark’ that forces us to rethink the timeline of vertebrate evolution

Living sharks are often portrayed as the apex predators of the marine realm. Paleontologists have been able to identify fossils of their extinct ancestors that date back hundreds of millions of years to a time known as the Palaeozoic period. These early “sharks,” known as acanthodians, bristled with spines. In contrast to modern sharks, they developed bony “armor” around their paired fins.

A recent discovery of a new species of acanthodian from China surprised scientists with its antiquity. The find predates by about 15 million years the earliest acanthodian body fossils and is the oldest undisputed jawed fish.

These findings were published in Nature on Sept. 28.

Fanjingshania renovata, an ancient 'Shark' from China is Humans' oldest jawed ancestor; the study has been published on Nature — Fig. 1 Life reconstruction of Fanjingshania renovata. (Image by ZHANG Heming)

Reconstructed from thousands of tiny skeletal fragments, Fanjingshania, named after the famous UNESCO World Heritage Site Fanjingshan, is a bizarre fish with an external bony “armor” and multiple pairs of fin spines that set it apart from living jawed fish, cartilaginous sharks and rays, and bony ray- and lobe-finned fish.

Examination of Fanjingshania by a team of researchers from the Chinese Academy of Sciences, Qujing Normal University, and the University of Birmingham revealed that the species is anatomically close to groups of extinct spiny “sharks” collectively known as acanthodians. Unlike modern sharks, acanthodians have skin ossifications of the shoulder region that occur primitively in jawed fish.

Fig. 3 Life reconstruction of Fanjingshania renovata. (Image by FU Boyuan and FU Baozhong)

The fossil remains of Fanjingshania were recovered from bone bed samples of the Rongxi Formation at a site in Shiqian County of Guizhou Province, South China.

These findings present tangible evidence of a diversification of major vertebrate groups tens of millions of years before the beginning of the so called “Age of Fishes” some 420 million years ago.

Fig. 4 Fragment of the pectoral dermal skeleton (part of a pectoral spine fused to shoulder girdle plate) of Fanjingshania renovata shown in ventral view. (Image by Andreev, et al.)

The researchers identified features that set apart Fanjingshania from any known vertebrate. It has dermal shoulder girdle plates that fuse as a unit to a number of spines—pectoral, prepectoral and prepelvic. Additionally, it was discovered that the ventral and lateral portions of the shoulder plates extend to the posterior edge of the pectoral fin spines. The species has distinct trunk scales with crowns composed of a row of tooth-like elements (odontodes) adorned by discontinuous nodose ridges. Peculiarly, dentine development is recorded in the scales but is missing in other components of the dermal skeleton such as the fin spines.

“This is the oldest jawed fish with known anatomy,” said Prof. ZHU Min from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences. “The new data allowed us to place Fanjingshania in the phylogenetic tree of early vertebrates and gain much needed information about the evolutionary steps leading to the origin of important vertebrate adaptations such as jaws, sensory systems, and paired appendages.”

From the outset, it was clear to the scientists that Fanjingshania’s shoulder girdle, with its array of fin spines, is key to pinpointing the new species’ position in the evolutionary tree of early vertebrates. They found that a group of acanthodians, known as climatiids, possess the full complement of shoulder spines recognized in Fanjingshania. What is more, in contrast to normal dermal plate development, the pectoral ossifications of Fanjingshania and the climatiids are fused to modified trunk scales. This is seen as a specialization from the primitive condition of jawed vertebrates where the bony plates grow from a single ossification center.

Unexpectedly, the fossil bones of Fanjingshania show evidence of extensive resorption and remodelling that are typically associated with skeletal development in bony fish, including humans.

“This level of hard tissue modification is unprecedented in chondrichthyans, a group that includes modern cartilaginous fish and their extinct ancestors,” said lead author Dr. Plamen Andreev, a researcher at Qujing Normal University. “It speaks about greater than currently understood developmental plasticity of the mineralized skeleton at the onset of jawed fish diversification.”

The resorption features of Fanjingshania are most apparent in isolated trunk scales that show evidence of tooth-like shedding of crown elements and removal of dermal bone from the scale base. Thin-sectioned specimens and tomography slices show that this resorptive stage was followed by deposition of replacement crown elements. Surprisingly, the closest examples of this skeletal remodelling are found in the dentition and skin teeth (denticles) of extinct and living bony fish. In Fanjingshania, however, the resorption did not target individual teeth or denticles, as occurred in bony fish, but instead removed an area that included multiple scale denticles. This peculiar replacement mechanism more closely resembles skeletal repair than the typical tooth/denticle substitution of jawed vertebrates.

A phylogenetic hypothesis for Fanjingshania that uses a numeric matrix derived from observable characters confirmed the researchers’ initial hypothesis that the species represents an early evolutionary branch of primitive chondrichthyans. These results have profound implications for our understanding of when jawed fish originated since they align with morphological clock estimates for the age of the common ancestor of cartilaginous and bony fish, dating it to around 455 million years ago, during a period known as the Ordovician.

These results tell us that the absence of undisputed remains of jawed fish of Ordovician age might be explained by under sampling of sediment sequences of comparable antiquity. They also point towards a strong preservation bias against teeth, jaws, and articulated vertebrate fossils in strata coeval with Fanjingshania.

“The new discovery puts into question existing models of vertebrate evolution by significantly condensing the timeframe for the emergence of jawed fish from their closest jawless ancestors. This will have profound impact on how we assess evolutionary rates in early vertebrates and the relationship between morphological and molecular change in these groups,” said Dr. Ivan J. Sansom from the University of Birmingham.

Press release from the Chinese Academy of Sciences

Keep Reading

Biology

Rare Fossil Teeth from China Overturn Long-held Views about Evolution of Vertebrates

By ScientifiCult 29 September 2022

Rare Fossil Teeth from China Overturn Long-held Views about Evolution of Vertebrates

An international team of researchers has discovered 439-million-year-old remains of a toothed fish that suggest the ancestors of modern osteichthyans (ray- and lobe-finned fish) and chondrichthyans (sharks and rays) originated much earlier than previously thought.

Related findings were published in Nature on Sept. 28.

Rare Fossil Teeth from China Overturn Long-held Views about Evolution of Vertebrates. Fig. 1 Life reconstruction of Qianodus duplicis. (Image by ZHANG Heming)

A remote site in Guizhou Province of south China, containing sequences of sedimentary layers from the distant Silurian period (around 445 to 420 million years ago), has produced spectacular fossil finds, including isolated teeth identified as belonging to a new species (Qianodus duplicis) of primitive jawed vertebrate. Named after the ancient name for modern-day Guizhou, Qianodus possessed peculiar spiral-like dental elements carrying multiple generations of teeth that were added throughout the life of the animal.

The tooth spirals (or whorls) of Qianodus turned out to be one of the least common fossils recovered from the site. They are small elements that rarely reach 2.5 mm and as such had to be studied under magnification with visible light and X-ray radiation.

A conspicuous feature of the whorls is that they contained a pair of teeth rows set into a raised medial area of the whorl base. These so-called primary teeth show an incremental increase in size towards the inner (lingual) portion of the whorl. What makes the whorls of Qianodus unusual in comparison with those of other vertebrates is the clear offset between the two primary teeth rows. A similar arrangement of neighboring teeth rows is also seen in the dentitions of some modern sharks but has not been previously identified in the tooth whorls of fossil species.

The discovery indicates that the well-known jawed vertebrate groups from the so-called “Age of Fishes” (420 to 460 million years ago) were already established some 20 million years earlier.

“Qianodus provides us with the first tangible evidence for teeth, and by extension jaws, from this critical early period of vertebrate evolution,” said LI Qiang from Qujing Normal University.

Unlike the continuously shedding teeth of modern sharks, the researchers believe that the tooth whorls of Qianodus were kept in the mouth and increased in size as the animal grew. This interpretation explains the gradual enlargement of replacement teeth and the widening of the whorl base as a response to the continuous increase in jaw size during development.

For the researchers, the key to reconstructing the growth of the whorls was two specimens at an early stage of formation, easily identified by their noticeably smaller sizes and fewer teeth. A comparison with the more numerous mature whorls provided the palaeontologists with a rare insight into the developmental mechanics of early vertebrate dentitions. These observations suggest that primary teeth were the first to form whereas the addition of the lateral (accessory) whorl teeth occurred later in development.

Fig. 2 Volumetric reconstruction of a tooth whorl viewed from its lingual side (holotype of Qianodus duplicis). The specimen is just over 2 mm in length. (Image by Zhu, et al.)

“Despite their peculiarities, tooth whorls have, in fact, been reported in many extinct chondrichthyan and osteichthyan lineages,”said Plamen Andreev, the lead author of the study. “Some of the early chondrichthyans even built their dentition entirely from closely spaced whorls.”

The researchers claim that this was also the case for Qianodus. They made this conclusion after examining the small (1–2 mm long) whorls of the new species with synchrotron radiation—a CT scanning process that uses high energy X-rays from a particle accelerator.

“We were astonished to discover that the tooth rows of the whorls have a clear left or right offset, which indicates positions on opposing jaw rami,” said Prof. ZHU Min from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences.

Fig. 3 Virtual section along the length of a tooth whorl in side view (holotype of Qianodus duplicis). The specimen is just over 2 mm in length (Image by Zhu, et al.)

These observations are supported by a phylogenetic tree that identifies Qianodus as a close relative to extinct chondrichthyan groups with whorl-based dentitions.

“Our revised timeline for the origin of the major groups of jawed vertebrates agrees with the view that their initial diversification occurred in the early Silurian,” said Prof. ZHU.

The discovery of Qianodus provides tangible proof for the existence of toothed vertebrates and shark-like dentition patterning tens of millions of years earlier than previously thought. The phylogenetic analysis presented in the study identifies Qianodus as a primitive chondrichthyan, implying that jawed fish were already quite diverse in the Lower Silurian and appeared shortly after the evolution of skeletal mineralization in ancestral lineages of jawless vertebrates.

“This puts into question the current evolutionary models for the emergence of key vertebrate innovations such as teeth, jaws, and paired appendages,” said Ivan Sansom, a co-author of the study from the University of Birmingham.

Press release from the Chinese Academy of Sciences about the fossil teeth overturning long-held views on the evolution of vertebrates

Keep Reading

Biology

Dawn of Fishes — Early Silurian Jawed Vertebrates Revealed Head to Tail

By ScientifiCult 29 September 2022

Dawn of Fishes — Early Silurian Jawed Vertebrates Revealed Head to Tail

A newly discovered fossil “treasure hoard” dating back some 436 million years to the early Silurian period reveals, for the first time, the complete body shape and form of some of the first jawed fishes.

The discovery was published in Nature on Sept. 28 by an international team led by Prof. ZHU Min from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences and Prof. Per E. Ahlberg from Uppsala University, as the cover story and one in a series of four papers in the same issue.

The Gnathostomata or jawed vertebrates, which include not only almost all the backboned animals you see in zoos and aquariums but humankind as well, have a mysterious origin. The so-called molecular clock, which deduces the age of the most recent common ancestor of two animals by evaluating the difference between the two sets of DNA, suggests that the most recent common ancestor of all modern jawed vertebrates lived 450 million years ago during the Ordovician period. As a result, the origin of jaws cannot be later than that.

However, the fossil record of jawed vertebrates only becomes abundant from the Early Devonian (~419 million years ago), i.e., the beginning of the “Age of Fishes.” Only in the past 10 years have scientists found several complete jawed fishes from the Late Silurian (~425 million years ago). Even so, these records are still more than 25 million years later than when jaws should have originated. The dearth of earlier fossils means that jawed vertebrates are a “ghost lineage” in the early Silurian.

The remarkable discovery of complete early Silurian jawed fishes is the result of 20 years of continuous effort by the authors searching for fossil fishes in all possible Silurian rock strata in China. The breakthrough was finally made in late 2020, when complete early Silurian fishes were found in Xiushan County, Chongqing.

LI Qiang and CHEN Yang, both co-authors and leaders of the fieldtrips, recalled their research:

“We remember it was a rainy day. We climbed a mountain ghat. At the 38^th turn we found a complete Silurian fish, which initiated an explosion of discoveries in this area in the next two years.”

Fig. 1 Life reconstruction of Xiushanosteus mirabilis (Image by ZHANG Heming)

The authors reported two species. The first one and the most abundant species was named Xiushanosteus mirabilis. It is a tiny, 3-cm-long placoderm or armored jawed fish. The flat and semicircular head, along with the trunk armor, are reminiscent of its jawless ancestors, but its paired fins and powerful tail made Xiushanosteus a much more capable swimmer.

First author ZHU You’an, associate research professor at IVPP and also an Uppsala University alumnus, said,

“As a placoderm expert, I am dazzled by the early age and completeness of Xiushanosteus. It is like a dream. A lot of the anatomical features make perfect sense; it was an ‘Oh, now I know’ moment in my career.”

Fig. 2 Life reconstruction of Shenacanthus vermiformis (Image by ZHANG Heming)

The second fish reported is named Shenacanthus vermiformis. Also very small, it is an early shark relative. However, all the sharks we know are covered in tiny scales, or at most small mosaic plates. Shenacanthus instead has prominent “shoulder armor” made of several large plates that completely encircle its body. This feature, thought to be exclusive in placoderms, provides a strong hint that the first cartilaginous fishes were armored, similar to placoderms.

“Only 20 years ago it was still believed that sharks are primitive and other jawed fish evolved from a shark-like archetype. Now with the discovery of Shenacanthus, we can finally make certain that the opposite is true,” said Prof. ZHU You’an.

“Previously we could only dream of such exceptional and early fossils,” said corresponding author Prof. Ahlberg. “However, they are more than curiosities; they are first and foremost crucial data to test—and either support or confound—our long-held hypotheses regarding the rise of our lineage.”

“The excavation continues to yield remarkable materials,” said Prof. ZHU Min, who led the project and is also a CAS academician. “The Chongqing Lagerstätte, like the Chengjiang and Jehol biotas, will become a world-famous paleontological heritage and will provide key evidence for how the extraordinary diversity of the jawed vertebrates we see today arose.”

Press release from the Chinese Academy of Sciences

Keep Reading