BIOLOGICAL SCIENCES DEPARTMENT
NEW RECORDS OF PTERIDOPHYTES AND GYMNOSPERMS FROM THE LOWER
CRETACEOUS (APTIAN) OF COLOMBIA
CAMILA MONJE DUSSÁN
Biology Degree Dissertation
Director: Santiago Madriñán Ph.D, Universidad de los Andes, Bogotá,
Colombia
Co-‐directors: Camila Martínez M.Sc, Smithsonian Tropical Research
Institute (STRI), Panamá
Ignacio Escapa Ph.D, Egidio Feruglio Paleontological Museum (Mef),
Trelew, Argentina
ABSTRACT
I.
INTRODUCTION
II.
MATERIALS AND METHODS
1.
Geology of the basin
1.1. Bermejo Group
1.1.1.
Yaví Formation
1.1.2.
Alpujarra Formation
1.2. Collected Specimens
2.
Laboratory technics
2.1. Stereoscopy, measurements, photography
2.2. Parastichies determination
III.
SYSTEMATIC DESCPRITION
1.
Pteridophytes
1.1 Filicopsidae
Insertae sedis
1.1.1
cf. Marsileaceae sp.
1.1.2
Cladophlebis
sp.
2.
Gymnosperms
2.1 Coniferae
Insertae sedis
2.1.1.
Brachyphyllum
sp.
2.1.2.
Podozamites vel Lindleycladus
sp.
2.1.3.
Araucarites
sp.
IV.
DISCUSSION
V.
CONCLUSIONS
ABSTRACT
The Mesozoic era was an essential time for plants evolution. Since, Pteridophytes and
Gymnosperms, the dominant groups by then, were considerably reduced due to the
expansion of Angiosperms by the end of that time. This way, the fossil record is the
most important tool for us to study those changes in diversity. Besides, knowing that
the tropics are the most diverse ecosystems on earth today, it is necessary to explore
their almost unknown fossil record, to understand the paleofloristic changes that have
took place in those specific groups until today. By means of systematic descriptions,
this study presents new records from the Lower Cretaceous (Aptian ca. 125-‐113 My)
flora of Colombia. The studied material was collected from the Upper Magdalena
Valley in four localities from the Tolima department at the Yaví and Alpujarra
formations. The fossil remains are from Pteridophytes and Gymnosperms specimens.
Among ferns, the one we should point out is a species from the morphogenus
Cladophlebis sp.
that includes sterile bipinnate fronds with lanceolate pinnule and
pecopteride venation. On the other hand, cf. Marsileaceae sp. includes sterile remains
of one leaflet with dichotomous, anastomosis venation and absence of middle and
marginal veins. The studied Gymnosperms, present vegetative structures associated
with reproductive organs. The most abundant sterile fragments were included in
Brachyphyllum
sp. due to morphologic characteristics and leaf phyllotaxy.
Additionally, other specimen was assigned to
Podozamites vel Lindleycladus
sp.
due to
characteristics such as dorsiventral flattened and elongated opposed leaves. Another
outlined presence is the one of isolated female strobilus and ovuliferous scales of
Araucarites
(Araucariaceae) type. The new findings represent a key aspect to
understand the biogeography of the mentioned groups and, simultaneously, they
extend the almost unknown diversity of the Colombian cretaceous.
I. INTRODUCTION
During the Mesozoic era, Pteridophytes and Gymnosperms were two groups of plants broadly spread, dominating Southern and Northern Hemispheres ecosystems. The
Pteridophytes dates their origin back to the Devonian, ca. 419 Million years ago. During this period, the fossil record shows remains of “fern-‐like” shaped plants due to the absence of both, megaphyll leaves and the distribution of vascular tissues in protostele and siphonostele (Raven). Later, this group of plants dominated the Carboniferous period (ca. 358-‐298 My) and part of the Mesozoic era (Taylor et al., 2009).
During the Permian big extinction (ca. 298-‐252 My), most of those Pteridophytes associated forms got extinct, others survived and many others cropped up at the beginning of the Triassic period (ca. 252-‐201 My). The oldest families remains that have been found from that period includes, permineralized stems, and impression of fertile and sterile structures of Marattiaceae, Gleicheniaceae, Guaireaceae and Osmundaceae (Tidwell et al., 1994).
The Osmundaceae is a very representative family not only because of its antiquity (ca. 298-‐252 My), but also because it is considered an intermediary family between
leptosporangiate and eusporangiate ferns (Escapa et al., 2012).
Gymnosperms origin dates back to the Middle Devonian (ca. 393 My) from extinct specimens known as progymnosperms (Taylor et al., 2009; Kenrick et al., 2004). Nonetheless, the fossil record shows that during the Mesozoic era, the Gymnosperms were the dominant group of plants even over Pteridophytes (Taylor et al., 2009). In that moment, more
gymnosperms families existed than the ones we know today (Miller, 1977).
Additionally, almost every family had a cosmopolitan distribution during the Mesozoic, opposite to what today is presented by families like Araucariaceae, which has a limited distribution towards the Southern Hemisphere (Dettman et al., 2005). Gymnosperms contain four big groups that have been recognized from the Mesozoic era to the present: Cycads, Ginkgoales, Pinales and Gnetophyta, all of them sharing a common structure: a naked seed (Conway, 2013). Hence, to understand the origin, evolution and phylogenetic
relationships between these groups, many studies have focused on the ovuliferous complex. (Taylor et al., 2009; Miller, 1982).
Currently, issues regarding Pteridophytes and Gymnosperms; their origin, their evolution and their considerable reduction towards the end of the Mesozoic era with the arrival of Angiosperms, are still an enigma.
This way, fossil record is the most useful tool for us to study these changes on
diversity. Besides, knowing that tropics are the most diverse ecosystems on earth nowadays, it is necessary to study their almost unknown fossil record to understand the paleofloristic changes that have took place from that moment to our days.
In Colombia, the Upper Magdalena valley located between the eastern and central cordilleras, towards the south of the Tolima department, presents an extension of outcrop from the Cretaceous period. Nevertheless, the study and the knowledge of these remains are scarce. The objective of this study is to describe the fossil flora of Pteridophytes and
Gymnosperms from the Alpujarra and Yaví Formations of the Upper Magdalena Valley to extend the diversity of the almost unknown Cretaceous period of Colombia.
II. MATERIALS AND METHODS
1. Geology of the basin
Towards the south of the Tolima department and the north of the Huila department, the Upper Magdalena Valley presented two sequences of facies, one that has a continental origin and other that has a marine origin, both of them corresponding to nine stratigraphic unities described by Carrillo & Flórez (1994). The succession starts with a decreasing grain size sequence that lays discordantly on volcanite and pyroclastic rocks (Carrillo & Flórez, 1994).
Both the studies of marine palynomorphs (Foraminifera and Dinoflagellate) by Vergara & Prössl (1993) and the one of lithological unities by Carrillo & Flórez (1994)
indicated that this sequence of facies was originated in a partially marine environment inside a lithological unity dominated by deposits of continental origin (Carrillo & Flórez, 1994; Vergara & Prössl, 1994; Macia et al., 1985).
Over this sequence of facies lays mudstones and lumaquelic limestone, indicating the entrance of the sea during the Aptian period. Finally, the sequence ends with a facie of Quartz Arenite of littoral origin over which lays a facie of black claystones and limestones (Carrillo & Flórez, 1994). In Figure 1, it’s shown the location of the Yaví and Alpujarra Formations and the geological unities of the area.
Figure 1. Geological map of the locality-‐type of the Bermejo Group in which are shown the localities where the fossil remains were found (Modified from Núñez & Rodríguez (1995)).
1.1 Bermejo Group
Bermejo Group is the name proposed by Carrillo and Flórez to group the Yaví and Alpujarra Formations in which the external morphology and internal structure of the layers present similar characteristics, which denotes an equal continental origin of decreasing grain size sequence (Carrillo & Flórez, 1994). The Bermejo Group limits discordantly on its base with pre-‐Cretaceous rocks from the Saldaña Formation and, on its roof, the Ocal Formation lays concordantly. This shows clear evidence of paleoenvironmental littorals that confirm the progress of the sea by the end of the Aptian (Carrillo & Flórez, 1994; Etayo-‐Serna et al., 1976). The deposit environments of the Bermejo Group go from alluvial fans of the Yaví Formation to alluvial and coastal plains of the Alpujarra Formation.
Figure 2. Depositional environments of the Bermejo Group (Taken from Carrillo & Flórez, 1994).
1.1.1 Yaví Formation
The name is used for the first time by Bernal et al (1976) and is formally established by Mojica & Macía (1981). The Yaví Formation is located on alluvial fans with low sinuosity and stream beds (Figure 2), it also presents relatively fast burial rates (Carrillo & Flórez, 1994). Concerning its lithology, it is composed by sandstones, mudstones and interspersing of conglomerates on the middle and high parts of the sequence (Carrillo & Flórez, 1994).
The presence of pollen from Callialasporites turbatus, Monosulcites spinosus and Afropollis sp. and spores from Cicatricosisporites purbeckensis, propose the Yaví Formation as Aptian (Vergara & Prössl, 1994). Likewise, the presence of the dinoflagellate Cribroperidinium intricatum reveals a connection between terrestrial and marine environments in the
Formation (Vergara & Prössl, 1994).
1.1.2 Alpujarra Formation
Alpujarra formation was proposed, by Carrillo & Flórez (1994), It is deposited from alluvial to coastal plains, presenting high sinuosity stream beds (meandering rivers) and low depositional rates (Figure 2). Its lithology is composed mainly by sandstones, mudstones and conglomerates in lower proportion (Carrillo & Flórez, 1994). There presence of tuffs reflects volcanic activity contemporary with the deposit (Carrillo & Flórez, 1994).
On its base, it limits with the Yaví Formation and on its roof with the Ocal Formation (Etayo-‐Serna et al., 1976). By overlapping principles and by presence of ammonites, bivalves and dinoflagellates (Mejía et al., 2012), the Alpujarra Formation is proposed as Aptian as well (Carrillo & Flórez, 1994).
1.2 Collected specimens
They were collected 113 fossil remains by Camila Martínez, Jorge Moreno, Catalina Suárez and Javier Luque in four localities of the Tolima department (Figure 1.). These remains include, 108 sterile and fertile macrofossils and 5 samples of microfossils (GPS data are found on the database of the Smithsonian Tropical Research Institute (STRI) and geographically referenced on Figure 1).
50 of the 108 macrofossils correspond to sterile fronds of Pteridophytes and 63 belong to sterile and fertile remains of Gymnosperms. 4 of the 5 microfossil samples belong to the Alpujarra Formation and one to the Yaví Formation. Additionally, fossil woods of different sizes from the Yaví Formation were collected.
The samples are store at the Universidad de los Andes Herbarium in Bogotá, Colombia, and were analyzed under the assistance of Ignacio Escapa Ph.D at the Egidio Feruglio
Paleontological Museum in Trelew, Patagonia, Argentina.
2. Laboratory technics
2.1 Stereoscopy, measurement and photography
The fossil remains that belong to Pteridophytes and Gymnosperms prints didn’t show preservation of cuticular characteristics and didn’t require any preparation.
The macrofossil description took place on the Egidio Feruglio Paleontological Museum (Mef). Fossils were analyzed using a Zeiss Stemi SV11 stereoscope and a Zeiss Stemi SV 11
For measures taking, a Mitutoyo digital gauge of 0-‐150 mm was used. For
Pteridophytes, we took register of: fronds, primary and secondary rachis, leaflets, pinules and primary and secondary veins. For Gymnosperms, the measurements were made over primary, secondary and tertiary branches and leaf size. Photographs were made with an 18 megapixels Canon Eos Rebel T2i/550D camera and for the processing and assembly of plates the program Adobe Photoshop CS5 was used.
2.2 Determination of parastichies
Phyllotaxis or leaf disposition along an axis in plants, is determined by counting the leaves that are located in every turn of the axis until the next leaf gets to be in line with the first one (Escapa & Cúneo, 2012).
In fossil plants, most of the times it is impossible to determine its phyllotaxis, and there is where we use parastichies: oblique rank of the leaves that climb on the left and right angle of an axis (Escapa & Cúneo, 2012).
To determine the number of parastichies, we had to use the sine function (reason between Y coordinate values) so we could find the angles at which the oblique ranks are climbing on right and left sides (Figure 3). For this, we can find the reason between the relative size of the leaf base (p) and the stem diameter (d) and calculate the angle for each side (α y β) (Figure 3)(Watson et al., 1987). This result is then used to calculate de number of parastichies that normally adjusts to numbers that correspond to the Fibonacci fractions. For example, if we have 5/8, it means that we need to circle the axis five times passing through eight leaves to get two leaves in line (Escapa & Cúneo, 2012; Watson et al., 1987).
Fibonacci fraction
Parastichy number
Parastichy number
# Spirals # Leaves passing throught
Figure 3. Parastichies determination (Modified from Escapa & Cúneo 2012 and Watson et al., 1987).
III. SYSTEMATIC DESCRIPTION
1. Division – Pteridophytes
1.1 Filicopsida Insertae sedis
1.1.1 Morphogenus – cf. Marsileaceae sp.
Type species: Marsileaceaephyllum johnhalii (Skog & Dilcher) Nagalingum comb. nov.
Remarks: cf. Marsileaceae sp. includes sterile remains of one leaf with dichotomous venation, partial anastomosis, absence of middle vein and presence or absence of collector marginal vein (Hermsen et al., 2013; Hu et al., 2008; Nagalingum, 2007). It was initially described as Marsilea johnhalii by Skog & Dilcher (1992) based on rhizomes and stalk with four terminal leaves of crenated to entire margin, dichotomous venation and anastomosis formation with a marginal vein and without fertile structures in organic connection.
Afterwards, Nagalingum (2007) suggested that vegetative remains of Marsileaceae type that haven’t been found in repeated association with sporocarps should be included in the Marsileaceaephyllum morphogenus (Taylor et al., 2009; Hu et al., 2008). Nonetheless, Hermsen and contributors (2013) propose that most of the diagnosis characteristics to assign specimens to Marsileaceaphyllum are wide and used in ambiguous ways.
This is why they limit the diagnosis of Marsileaceaphyllum only to sterile fronds with four obovated to obteldoided shaped leaves, which means that is advisable to include found specimens with less leaves and venation patterns with few preservation in cf. Marsileaceae sp. (Hermsen et al., 2013).
Marsileaceae is a leptosporangiate and heterosporic fern family whose characteristics are dichotomous venation, absence of middle vein and anastomosis formation. This last characteristic, together with the areoles shape, allows us to differentiate Marsileaceae from other fern groups that also present the absence of a prominent middle vein (Nagalingum, 2007).
This way, different characteristics in venation patterns and leaves organization observed in cf. Marsileaceae sp. permit us to think of this species as a fossil representative of this family.
Regarding leaflets number and position, they can be: 4 cross shaped leaflets common in extant Marsilea and in fossil specimens Marsileaceaephyllum johnhalii, Marsileaceaephyllum sp. A (Rich et al., 2001) and Marsileaceaephyllum sp. C (Nagalingum, 2007). Additionally 2 opposite leaflets can be found in extant Regnellidium and in the fossil Regnellites nagashimae (Nagalingum, 2007).
In terms of venation patterns, some modifications have been observed between fossil specimens and extant representatives such as presence or absence of marginal vein and the place on the leaf where anastomosis takes place (Nagalingum, 2007). Nonetheless, vegetative isolated characters are not enough to determine the taxonomic affinity of Marsileaceae fossils. This is why the presence of reproductive structures is necessary to assign those remains to natural groups (Cúneo et al., 2013; Nagalingum, 2007; Collinson, 1996).
cf. Marsileaceae sp. Figures 1 and 2 Locality: 110017
Age: Lower Cretaceous (Aptian)
Specimens: STRI 34049, 34051, 34052, 34053
Description: Sterile fragments of one isolated leaf of at least 2 cm in length (incomplete) and 4 cm in width (incomplete). The best preserved samples present entire margin. The leaves are flabellate shaped since in most of them, the apex is rounded with an angle greater than 90° and its base shape is somewhere between concave and truncated. There’s no presence of a primary vein but of many veins that apparently have its origin on one same point.
The veins are sinuous and extend from the base to the apex. Every one of them grows in different angles between 0º and 90º and some of them divide near the margin while others divide on the middle and near the leaf base. In most of the veins of the studied samples, two bifurcations take place.
Some of the veins form anastomosis, usually on 1/3 of the distal part, thus developing elliptic and obovate areoles, but due to the lack of good preservation of other veins, it was impossible to observe if the anastomosis takes place and, if it does, where does it happen. There’s not a visible marginal vein in the studied specimens.
Remarks: The materials describe in here have been assigned to the morphogenus cf. Marsileaceae sp. based on characters such as an sterile leaflet with dichotomous venation, partial anastomosis and absence of both middle and marginal collecting veins.
cf. Marsileaceae sp. is morphologically comparable with five taxa that have been assigned inside Marsileaceaephyllum: Marsileaceaephyllum sp B and Marsileaceaephyllum lobatum described by Nagalingum (2007) from Albian of Antarctica, Marsileaceaephyllum sp. C (Nagalingum) from Albian of Australia, Marsileaceaephyllum sp. A of Rich et al (2001) from the Eocene of USA and Marsileaceaephyllum mahisensis described by Hu, Taylor, Brenner et Basha (2008) from the Albian of Jordan. Additionally, it is similar to sterile structures of Regnellites nagashimae (Yamada & Kato) species from the Upper Jurassic– Lower Cretaceous of Japan and with two South American species from the Campanian– Maastrichtian of
1) STRI 34053. Fragment of 1 steril lea let with dichotomizing
venation and labellate form. Scale 1 cm.
2) STRI 34052. Fragment of 1 sterile lea let with dichotomizing
venation. Scale 1 cm.
cf. Marsileaceae sp.
12
Argentina, Mirasolia irupensis and Regnellidium thomas-‐taylorii Hermsen, Gandolfo & Cúneo (2013).
cf. Marsileaceae sp. is similar to R. nagashimae in terms of the leaf’s shape and margin and the absence of the marginal vein. Nonetheless, we were able to observe subtle differences regarding the number of leaves, some general dimensions and the venation pattern.
In contrast, it is similar to M. johnhallii Skog & Dilcher (1992) regarding its venation pattern, its dimensions and its leaf’s margin. It is similar to Marsileaceaephyllum sp. B Nagalingum species in characters such as its leaf’s margin and its venation pattern while in characters such as the absence of a marginal vein and its leaves dimensions it’s similar to M. lobatum Nagalingum.
On the other side, we could observe huge differences between cf. Marsileaceae sp. and the South American species Mirasolita irupensis and Regnellidium thomas-‐taylorii given that the only character that it shares with M. irupensis is the margin of its leaves.
This way, for a right determination of taxonomic affinities in Marsileaceae fossils, the presence of spores or sporocarps is necessary given that the vegetative characters are insufficient for that allowance. Therefore, the collected fossil remains are considered as possible Marsileaceae fossils due to architecture characters and leaves morphology such as venation pattern.
1.1.2 Morphogenus – Cladophlebis
Type species: Cladophlebis albertsii (Dunker) Brongniart, 1849
Remarks: Cladophlebis includes remains of sterile at least bipinnate fronds with lanceolate pinules completely inserted from the base and with venation that cannot be assigned to a natural group due to the absence of reproductive characters (Escapa & Cúneo, 2012 ;Phipps et al., 1998 and works mentioned in there).
Cladophlebis was proposed by Brongniart in 1849 to designate only sterile fronds of filiform aspect from the Mesozoic, and afterwards, most of them have been alternatively related with different ferns families such as Osmundaceae, Cyatheaceae and Schizaeaeceae (check on Carrizo et al., 2011). This allows us to evidence the uncertain systematic affinity of this morphogenus with natural groups and simultaneously suggests the development of vegetative homoplasious morphologies in different fern families (Escapa & Cúneo, 2012).
Given that Brongniart did not propose a formal diagnosis, authors such as Herbst (1971), Harris (1961), Frenguelli (1947), Schimper (1874), and Saporta (1873) established characters that could give a clearer definition of that morphogenus (Carrizo et al., 2011; Berry, 1919).
Fronds affinity from the Cladophlebis type with natural groups is established from the findings of the vegetative organs in organic connection (or repeated association) with
reproductive structures and permineralized stems and/or rhizomes. These organs have enough unique characters for include them with certainty in one or other of the mentioned families.
Cladophlebis sp. Figures 1–3 Locality: 110017
Age: Lower Cretaceous (Aptian)
Specimens: STRI 31315, 34042, 34043, 34044, 34046, 34050, 34054
Description: Sterile al least bipinnate fronds fragments with variable measures of up to 6 cm long (incomplete) and 12 cm width (Figures 1–3). It presents a straight rachis of up to 8 mm width on its base and diminishing to the apex, ridged by a longitudinal stretch mark (Figure 1).
The pinnas arrangement generally goes from opposite to sub-‐opposite, in its majority towards the base of the frond and alternate to the apex (Figures 1–3). They are inserted in angles between 60° and 90° increasing towards the base of the frond (Figure 1). The width of the secondary rachis or pinna rachis (of at least 0.32 mm to 1.58 mm), just as the one of the primary rachis, decreases towards the apex. The distance between adjacent pinnas is of up to 1 cm.
It is possible to observe a significant superposition between adjacent pinnas usually towards the basal portion of the frond, given that the abaxial side of a pinule completely overlaps on the adaxial side of the confronted pinule (Figure 1). The pinules shape of the observed specimens are elliptic (distal), ovate (proximal) and with entire margin (Figure 2). They are usually arrange in an opposite and sub opposite way on the proximal side of the pinna and alternately on the distal side and are perpendicularly inserted to its rachis.
The best preserved pinules presented measures of at least 1 mm length x 0.9 mm width and up to 6 mm length x 2 mm width. We observed a superposition between adjacent pinules who were distanced from each other on up to 0.4 mm. The middle vein extents straightly approximately on ¾ parts of the pinule where it skews just once (Figures 2 and 3). The secondary veins have their origin from the primary vein in sub opposite
arrangement with angles varying between 25° and 60°, and the most acute of them were mostly related to the distal side of the pinule. Most of the secondary veins skew at least twice: the first division takes place near the primary vein where elliptic and obovate areoles are sometimes formed; the second division and –when it actually takes place too-‐ third division, take place near the pinule margin where in some veins an anastomosis pattern is formed.
Remarks: The previously described materials have been included in Cladophlebis based on characters such as sterile bipinnate fronds, opposite disposed pinnas perpendicularly inserted to the primary axis, pecopterid pinules and dichotomous venation of the secondary veins. Regarding characters such as arrangement and insertion angle of the pinnas, pinules margin and morphology and insertion of both middle and secondary veins, Cladophlebis sp. is morphologically comparable with the sterile fronds of Todites cacerei from the Jurassic of the Patagonia, Argentina described by Escapa & Cúneo (2012). We could also find similarities on the general dimensions of the pinules, while the biggest differences are seen on the number of skews of the secondary veins.
Additionally, it is similar to Jurassic species from Yorkshire C. haiburnensis (L. & H.) Brongniart and C. aktashensis Turutanova-‐Ketova (Harris, 1961) in arrangement and insertion angle of the pinnas, pinules margin and number of skews of the lateral veins. In contrast, huge differences are observed regarding the dimensions of the pinules.
With C. roesserti (Schenk) Saporta, characters such as pinule margin and general morphology and insertion of both middle and secondary veins are comparable with the description of specimens of C. sp. The specie Kuklia exilis (Schizaeceae) shares some of the morphological characters such as arrangement and insertion of the pinnas, pinules margin and insertion angle of the secondary veins. Nonetheless, it is important to remember that this is a tripinnate species, in contrast with the bipinnate fronds of Cladophlebis sp.
On the other side, the adjacent pinules of K. exilis are usually connected thorough an intercalary tissue (Harris, 1961), a character that hasn’t been observed in this particular morphogenus.
1) STRI 31315. Fragment of sterile frond at least bipinnate
showing broad raquis ridged by longitudinal stretchmarks.
Scale 1 cm
2) STRI 34044. Fragment of sterile frond showing alternate pinnae
in the apex. Scale 1 cm.
3) STRI 34046. Fragment of sterile frond showing subopposite
arrangement of pinnae. Scale 1 cm.
arrangement of pinnae. Scale 1 cm.
12 3
Cladophlebis
Given that the frond affinities of Cladophlebis are established from findings of
vegetative organs in organic connection, usually this morphogenus is suggested as a possible Osmundaceae because sporangia of this family have been found in species of Todites
(Cladophlebis) and in an association of Cladophlebis with Osmundacaulis (Miller, 1971). Nonetheless, this association can be interpreted as a circumstantial event given the wide distribution and amazing abundance of Cladophlebis during the Mesozoic (Miller, 1971).
2. Division – Gimnospermae
2.1 Coniferales Insertae sedis
2.1.1 Morphogenus – Brachyphyllum
Species type: Brachyphyllum mamillare Linder & Hutton ex Brongniart, as designated by Harris (1979).
Remarks: Brachyphyllum and Pagiophyllum are two artificial morphogenera that have been assigned to sterile remains of Mesozoic Conifers with rhomboid to oval leaves, disposed in spiral and imbricated. The distinction between the morphogenera lies mostly in the relation between the length and the width of the leaves, while in Brachyphyllum they are more wide than long, in Pagiophyllum it is exactly the opposite way (Escapa & Cúneo 2012; Harris, 1979). Brachyphyllum was define initially by Brongniart in 1828, afterwards Linder & Hutton described the species Brachyphyllum mamillare in 1836, but Kendall was the one who
proposed the formal diagnosis of the morphogenera in 1947, emphasizing in cuticular characters from the vegetative structures (Harris, 1979).
Vegetative remains of Brachyphyllum type have been alternately related with many Conifer families like Araucariaceae, Cupressaceae, Taxodiaceae, Podocarpaceae and
Cheirolepidiaceae (Du et al., 2013; Passalia, 2009; van der Hammer et al., 2003; Stockey, 1994; Bose & Banerji, 1984; Alvin, 1982; Stockey, 1982). In this case, the possible affinities of
Brachyphyllum with natural groups have been established from findings of morphological characters associated with fertile structures and/or preserved epidermal characters (Du et al., 2013).
Brachyphyllum sp. Figures 1–3 Locality: 110011 and 110014
Age: Lower Cretaceous (Aptian)
Specimens: STRI 27213, 27220, 27232, 29957, 29958
Description: Vegetative fragments of at least two and three orders of magnitude (Figures 1 and 2). Primary axis (incomplete) of up to 8 cm length and 3 mm width (with leaves), with an apparently orthotropic growth. Secondary axis (incomplete) of up to 2.5 cm length and at least 2 mm width (with leaves) is inserted mostly in angles of 60° and with alternatively disposition (Figure 1). The distance between adjacent branches is up to 2 cm and there is no superposition between them. The third magnitude order of up to 1.5 cm length and at least 2 mm width (diminishes towards the apex) inserts in right angles (towards the base) and acute angles (towards the apex) with opposite and sub opposite arrangement (Figure 1). There is no superposition.
Persistent leaves with complete margin, imbricated, spirally disposed and usually adpressed to the primary, secondary and tertiary axis (Figures 2 and 3). With rhomboid aspect (the ones of the base usually have a circular aspect), slightly wider (up to 1.6 mm) than large (up to 1.3 mm) on the secondary and tertiary axis, and longer (2.19 mm) than wide (1.23 mm) on the primary axis (Figure 3). Parastichies 5/7 on the first order branch and 5/6 on the second and third order branch. Towards the distal side of the axes, some leaves present an apex with open arrangement, dislodging in angles between 25° and 30° (Figure 3).
While the apex on the leaves of the primary axis is acuminate and has a rounded base, the leaves from both the secondary and tertiary axis are obtuse and have a convex apex and base (Figures 1–3). Cuticular and venation characters are not preserved.
Remarks: The previously described materials have been included in Brachyphyllum basing on characters such as apparently rhomboid, imbricated, spirally disposed, adpressed and wider than longer leaves (Du et al., 2013; Stockey, 1982; Harris, 1969).
Brachyphyllum sp. is morphologically comparable with the Jurassic species Brachyphyllum mamillare (Harris, 1979), Brachyphyllum ardenicum (Harris, 1979),
Brachyphyllum crucis Kendall (Harris, 1979), Brachyphyllum pulcher (Lorch, 1968), Brachyphyllum porrigente (Lorch, 1968) and Brachyphyllum negevensis (Lorch, 1968) considering the spiral arrangement and the rhomboid shape of the leaves.
They can be differentiated mainly on the number of parastichies and on the leaves dimensions because the ones of the Brachyphyllum sp. are smaller than the ones of the Jurassic species.
The Jurassic Argentinian Brachyphyllum cf. lotenaense (Escapa & Cúneo, 2012) species share many characters with the previously mentioned species such as parastichies number, rhomboid shape and complete margins on its leaves. We could observe subtle differences regarding dimensions and only foliar phyllotaxy.
In contrast, with the Cretaceous species Brachyphyllum ningshiaense Chow & Tsao (Du et al., 2013), Brachyphyllum obesum (Yabe & Kubota, 2004), Brachyphyllum obtusum Chow & Tsao (Du et al., 2013), Brachyphyllum castatum (Watson et al., 1987), Brachyphyllum
crassifolium (Bosma et al., 2009), Brachyphyllum squammosum (Bosma et al., 2009),
Brachyphyllum sp. 1 (Watson et al., 1987) and Brachyphyllum sp. 2 (Watson et al., 1987), we could observe similarities regarding the leaves disposition (imbricated and spiraled) and entire margins. Rhomboid shapes and parastichies 5/8 are not common between Cretaceous species.
Additionally, regarding foliar dimensions, we could observe a significant variation given that the sizes we found were of at least 1.1 mm and up to 14 mm length and at least 0.9 mm and up to 8 mm width.
2.1.2 Morphogenus – Podozamites vel Lindleycladus
Species type: Zamia lanceolata Lindley & Hutton 1836
Remarks: Podozamites vel Lindleycladus includes sterile remains of simple leaves of
lanceolate aspect, with an opposite to helicoid arrangement and with parallel veins that skew on its base and converge towards the apex (Harris, 1979).
In 1836, Lindley & Hutton initially designated Zamiaceae aspect specimens as Zamia lanceolata, but afterwards they were described as Podozamites lanceolatus by authors such as Braun (1843) & Seward (1900). Nonetheless, the mentioned names have not been accepted given that a formal diagnosis hasn’t been proposed.
Podozamites and Lindleycladus belong to different genus that can only be
microscopically distinguished (Harris, 1979). The differences between both morphogenera lies mostly in cuticular characters, while in Podozamites the stomata are transversally oriented, in Lindleycladus they are longitudinally disposed (Kunsmann, 2004; Harris, 1979). On the other side, there are subtle differences regarding morphological characters in vegetative remains. Lindleycladus presents the widest part of its leaf towards its inferior side, contrary to Podozamites, a specimen where the widest part of its leaf is located towards the central part of the leaf. Regarding venation characters of Podozamites, there is a vein every 2 mm, while in Lindleycladus, a vein is found every 3 mm (Weber, 1968).
The sterile remains affinity of Podozamites vel Lindleycladus is established basing on findings of vegetative organs in repetitive association with reproductive structures and with enough cuticular characters so the non-‐ambiguous inclusion inside the previously mentioned genus is possible.
Podozamites vel Lindleycladus sp. Plate D, Figure 4
Locality: 110011
Age: Lower Cretaceous (Aptian)
Specimens: STRI 27194, 27224
Description: Sterile isolated branch fragment of up to 3 cm length (incomplete) x 2.5 cm width (incomplete). It presents a primary axis of up to 2.5 mm width (incomplete) ridged by longitudinal stretch marks. The leaves are usually inserted in up to 70° angles, have an opposite and –occasionally-‐ sub opposite arrangement. They have an elliptical shape,
elongated up to 2 cm length and at least 5 mm width (on the middle of the leaf), dorsiventrally flattened, entire margin and resupinated on the base of the leaves.
Both the apex and the base have a convex and obtuse shape. The distance between adjacent leaves goes from 5 mm to 1 cm. There is not an apparent superposition between them. There is no presence of a middle vein but it has a parallel venation and we could observe that, apparently, there were 3 veins every mm.
Remarks: The previously described materials have been included in Podozamites vel
Lindleycladus based on characters such as simple, lanceolate, dorsiventrally flattened, slightly stalked and contracted base leaves. Numerous veins of parallel aspect skewed on its base and convergent towards the apex.
Podozamites vel Lindleycladus is morphologically comparable to the Jurassic Yorkshire’s Lindleycladus lanceolatus species due to its simple leaves with opposite disposition, entire margins and parallel veins that converge to the apex. We could observe differences regarding general leaf dimensions and foliar base characters. With the Colombian species Podozamites sp., it resembles regarding shape and general dimensions of its leaves and venation patterns. It presents subtle differences in morphological characters from the foliar base.
2.1.3 Morphogenus – Araucarites Presl
Species type: Araucarites goeppertii Presl, en Sternberg 1838
Remarks: Araucarites includes ovuliferous isolated complexes of Araucariaceae affinity (Escapa & Cúneo, 2012; Rees & Cleal, 2004).
Araucarites was initially proposed in 1837 by Endlicher as a morphogenus to exclusively designate permineralized tree trunks from the Carboniferous (Escapa & Cúneo, 2012). Afterwards, in 1838, Press uses the name Araucarites for cones with megasporagium and vegetative axes of Araucariaceae affinity (Escapa & Cúneo, 2012). Many authors have proposed the inclusion of only isolated complexes that do not present ligule in Araucarites and in Araucaria when the ligule is visible (Escapa & Cúneo, 2012; Rees & Cleal, 2004; Bose & Maheshwari, 1973).Nonetheless, many other authors have proposed that the presence or absences of ligule lies mostly in both the abaxial or adaxial face that is being observed and in the specimen preservation (Escapa & Cúneo, 2012). Having this in mind, there are strong doubts in the usage of the mentioned names, so it is important to say that in this work the Araucarites name, as Rees & Cleal (2004) suggest, will be used only to designate ovuliferous isolated complexes of Araucariaceae affinity that does not present cuticular characters that allow us a precise and not an ambiguous designation.
Araucarites sp. Figures 1 and 2 Locality: 110011 y 110014
Age: Lower Cretaceous (Aptian)
Specimens: STRI 27204, 27206, 27217, 27193
Description: Ovuliferous isolated complexes of 8.5 to 17 mm length. The widest portion lies on the distal side that is between 8 and 13 mm, diminishing gradually towards the proximal side that is between 4 and 6 mm width (Figures 1 and 2).
They have an obovate shape, a mucronate apex and a truncated base. Apparently, only one ovule is imbibed inside the middle region of the complexes (Figure 2) with variable measures between 6 and 12 mm length and 4 and 6 mm width on the distal side.
It also decreases towards the proximal side of the scale. The wings of up to 2 mm width are located on each side of the ovule (Figures 1 and 2).
Remarks: The previously described material is included inside Araucarites based on characters such as ovuliferous isolated complexes, dorsiventrally flattened, mucronate apex and just one seed located on the middle of the complex.
Araucarites sp. is morphologically comparable with the Jurassic specie Araucarites sp (Escapa & Cúneo, 2012) given the presence of only one seed inserted in the central part of the complex, the general dimensions and its morphological characters. It is differenced mainly on the general dimensions of the complex, becoming a smaller species compared to the one that is described on this work.
Araucarites sp. is differenced from Araucarites phillipsii (Harris, 1979) based on the size and the proportion of the wings that are disposed on each side of the seed, the general size of the complex and the seed and the presence of both cuticule and ligule.
On the other side, with Araucarites cf. cutchensis (Rees & Cleal, 2004) it shares characters such as general dimensions and proportions of the seed, mucronate shaped apex and obovate-‐ovate shaped seed.
The affinities of the ovuliferous isolated complexes with natural groups are
established based on the cuticular preserved characters, which possess enough characters to let us establish more precise comparisons and less ambiguous designations.
IV. DISCUSSION
The Cretaceous flora towards the south of the Tolima department is characterized by the presence of ferns and Gymnosperms, of whom we can highlight the Conifers. One of the most notorious characteristics of the flora is the absence of reproductive organs in organic connection or repetitive association with vegetative structures. This is the reason why those previously described remains are include in morphogenera, given that reproductive
structures possess enough characters that allow the non-‐ambiguous designation to natural groups.
The localities on the Yaví formation present particular and new elements for the Colombian Cretaceous flora. In them, we can distinguish the presence of a possible aquatic fern cf. Marsileaceae sp. of affinity with the fern family leptosporangiate and heterosporic Marsileaceae as the first register for the Lower Cretaceous in Colombia. Additionally, in general terms, this formation presents a wide abundance of Cladophlebis of possible affinity with Osmundaceae given that the 50 collected and 44 studied samples belong to that morphogenus.
Besides, on the localities of the Alpujarra formation, the Conifers represent the most abundant group given that there is no register of ferns in this formation. In the morphogenera that constitute this formation, we find Brachyphyllum and Araucarites as some possible Araucariaceae and Podozamites vel Lindleycladus with possible affinity with Podocarpaceae. The distribution of most of the current families of the Pteridophytes group is located in the tropic, this is why many authors have suggested it as their original place and the
diversification place to other parts of the world (Skog, 2001 and works they mention in there). In the particular case of this study, we identified two morphogenera of possible
affinity with Osmundaceae and Marsileaceae. Regarding Osmundaceae is considered that the origin and diversification of this family, currently represented by Todea, Osmunda and
Leptoteris genera, is located on the Southern Hemisphere towards the end of the Permian and beginnings of the Triassic (Escapa et al., 2012; Skog, 2001; Phipps et al., 1998).
Nonetheless, currently it presents a cosmopolitan distribution except on cold and desert zones, and anyway it possess an abundant fossil register during the Mesozoic at a
global level global (Escapa et al., 2012; Skog, 2001). Particularly, the biggest density is found during the Middle-‐Upper Jurassic period on both Hemispheres (Skog, 2001; Escapa et al., 2012).
During the Lower Cretaceous the Osmundaceae kept on being stable regarding the fossil register on both Southern and Northern Hemispheres even though there is a register of a big decline for a great number of macrofossils and microfossils of Pteridophytes towards the Lower Cretaceous (Skog, 2001). This way, it is necessary to emphasize that of the collected specimens, the ones that are related to the mentioned family are the most abundant forms of Pteridophytes in the Upper Magdalena Valley.
The Marsileaceae family is currently represented by Regnellidium, Marsilea and
Pilularia. The last two present a cosmopolitan distribution, while Regnellidium is only found in the Southern Hemisphere (Cuneo et al., 2013). Based on its fossil register, it extents towards the upper Jurassic in the Northern Hemisphere, this is why many authors suggest that a possible origin place is towards Northern latitudes, migrating afterwards towards the south during the Cretaceous (Skog, 2001).
The most abundant registers are found towards the Middle Cretaceous, an epoch that was initially considered to be the possible origin of the aquatic ferns (Yamada & Kato, 2002; Skog, 2001). Regarding South America, we only have register of this family in the Argentinian and Brazilian Upper Cretaceous. Following this, it’s interesting to mention that the
morphogenus that is described in this work would represent the first register for the Lower Cretaceous in Colombia.
Nevertheless, given the absence of enough vegetative and reproductive characters, it’s impossible to confirm this with certainty. Anyway, if we can reaffirm what we suggested, we would open the possibility of important phylogenetic and paleobiogeographic studies for us to understand the history and the origin of aquatic ferns.
Regarding the Conifers, the affinity of two morphogenera to the Araucariaceae and Podocarpaceae families is suggested. The possible presence of these two families represents an interesting fact given that they evidence the relict of the Conifers that survived until today and that nowadays present a restricted distribution on the Southern Hemisphere.
This in contrast with what the fossil register shows during the Mesozoic, time when the Conifers represented the dominant flora and were widely distributed on both
Hemispheres (Escapa et al., 2012; Miller, 1997). Currently, the Araucariaceae family is
towards the Southern Hemisphere. Nonetheless, the fossil register evidences that the family was extent even to the Northern Hemisphere during the Mesozoic (Escapa et al., 2012; Dettman & Clifford, 2005).
The Araucariaceae family dates back to the Lower Cretaceous with an abundant and diverse fossil register of the Araucaria. Nonetheless, the general belief says that its
diversification goes until de Cretaceous-‐Paleogene given that the evidence shows an
acceleration in the diversity of both Araucaria and the fossil register of Agathis and Wollemia (Dettman & Clifford, 2005).
The origin of the family is considered to be centered on the Southern Hemisphere given the wide abundance and diversity of Araucaria remains that have been found in Australia and in La Patagonia, Argentina (Escapa et al., 2012). According to all this, the
diversification of the family Araucariaceae took place during the Cretaceous, which means we should highlight that considering the studied Lower Cretaceous’ specimens from Tolima, the Brachyphyllum and Araucarites morphogenera of possible affinity with Araucariaceae are the most abundant forms, suggesting thus that the south of the Tolima department as a possible diversification center of the family in Colombia given that there are not previous registers of these forms in the country.
The Podocarpaceae family is currently represented by about 18 genera, of which we should emphasize on Podocarpus and Dacrydium, the two genera that contain more species (Hill, 1994). The history of the family extents towards the Upper Triassic of Africa and their widest diversity is registered during the Jurassic and the Cretaceous in the Southern
Hemisphere.
Nevertheless, the fossil register shows that the Podocarpaceae extent to small zones of the Northern Hemisphere during the Mesozoic (Miller, 2010). Likewise, nowadays, just like Araucariaceae, its distribution is restricted only to the Southern Hemisphere (Miller, 2010). There is evidence in the Cretaceous of Colombia of vegetative remains, although they are not that abundant or diverse. What we observed through the comparisons we made between every morphogenera with representative from the Mesozoic of both Southern and Northern Hemisphere shows that the Lower Cretaceous’ paleoflora of the Tolima department is similar to taxon of both Hemispheres.
Regarding ferns, cf. Marsileaceae sp. is morphologically comparable with Regnellites nagashimae from the Jurassic of Japan, while Cladophlebis sp. is similar to Todites cacerei from the Jurassic of Argentina.
